Oligoribonucleotides and ribonucleases for cleaving RNA

ABSTRACT

Oligomeric compounds including oligoribonucleotides and oligoribonucleosides are provided that have subsequences of 2′-pentoribofuranosyl nucleosides that activate dsRNase. The oligoribonucleotides and oligoribonucleosides can include substituent groups for increasing binding affinity to complementary nucleic acid strand as well as substituent groups for increasing nuclease resistance. The oligomeric compounds are useful for diagnostics and other research purposes, for modulating the expression of a protein in organisms, and for the diagnosis, detection and treatment of other conditions susceptible to oligonucleotide therapeutics. Also included in the invention are mammalian ribonucleases, i.e., enzymes that degrade RNA, and substrates for such ribonucleases. Such a ribonuclease is referred to herein as a dsRNase, wherein “ds” indicates the RNase&#39;s specificity for certain double-stranded RNA substrates. The artificial substrates for the dsRNases described herein are useful in preparing affinity matrices for purifying mammalian ribonuclease as well as non-degradative RNA-binding proteins.

CROSS REFERENCED TO RELATED APPLICATIONS

[0001] This application is a continuation in part of U.S. Ser. No.08/659,440 filed Jun. 6, 1996.

FIELD OF THE INVENTION

[0002] This invention is directed to the synthesis and use of oligomericcompounds, including oligoribonucleotides and oligoribonucleosides,useful for strand cleavage of target RNA strands. Included in theinvention are oligoribonucleotides having modified sugars, bases orphosphate backbones and oligoribonucleosides having standard sugars andbases or modified sugars and bases linked together via non-phosphatebackbones. Further included in the invention are chimericoligoribonucleotides and oligoribonucleosides having mixed backbones,either phosphate or non-phosphate. Also included in the invention aremammalian ribonucleases, i.e., enzymes that degrade RNA. Such aribonuclease is referred to herein as a dsRNase, wherein “ds” indicatesthe RNase's specificity for certain double-stranded RNA substrates. Theoligoribonucleotides, oligoribonucleosides, ribonucleases andribonuclease substrates of the invention are useful for therapeutics,diagnostics and as research reagents.

BACKGROUND OF THE INVENTION

[0003] Oligonucleotides are known to hybridize to single-stranded DNA orRNA molecules. Hybridization is the sequence-specific base pair hydrogenbonding of nucleobases of the oligonucleotides to nucleobases of targetDNA or RNA. Such nucleobase pairs are said to be complementary to oneanother.

[0004] The complementarity of oligonucleotides has been used forinhibition of a number of cellular targets. Such complementaryoligonucleotides are commonly described as being antisenseoligonucleotides. Various reviews describing the results of thesestudies have been published including Progress In AntisenseOligonucleotide Therapeutics, Crooke, S. T. and Bennett, C. F., Annu.Rev. Pharmacol. Toxicol., 1996, 36, 107-129. These oligonucleotides haveproven to be very powerful research tools and diagnostic agents.Further, certain oligonucleotides that have been shown to be efficaciousare currently in human clinical trials.

[0005] To date most oligonucleotides studied have beenoligodeoxynucleotides. Antisense oligodeoxynucleotides are believed tocause a reduction in target RNA levels principally through the action ofRNase H, an endonuclease that cleaves the RNA strand of DNA:RNAduplexes. This enzyme, thought to play a role in DNA replication, hasbeen shown to be capable of cleaving the RNA component of the DNA:RNAduplexes in cell free systems as well as in Xenopus oocytes. Rnase H isvery sensitive to structural alterations in antisense oligonucleotides.This sensitivity is such that prior attempts to increase the potency ofoligonucleotides by increasing affinity, stability, lipophilicity andother characteristics by chemical modifications of the oligonucleotidehave often resulted in oligonucleotides that are no longer substratesfor Rnase H. In addition, Rnase H activity is quite variable. Thus agiven disease state may not be a candidate for antisense therapy onlybecause the target tissue has insufficient Rnase H activity. Thereforeit is clear that effective terminating mechanisms in addition to Rnase Hare of great value to the development of therapeutic and other agents.

[0006] Several publications describe the interaction of Rnase H andoligonucleotides. A recently publication is: Crooke, et. al., Biochem.J., 1995, 312, 599-608. Other earlier papers are: (1) Dagle et al.,Nucleic Acids Research, 1990, 18, 4751; (2) Dagle et al., AntisenseResearch And Development, 1991, 1, 11; (3) Eder et. al., J. Biol. Chem.,1991, 266, 6472; and (4) Dagle et al., Nucleic Acids Research, 1991, 19,1805. According to these publications, DNA oligonucleotides having bothunmodified phosphodiester internucleoside linkages and modifiedphosphorothioate internucleoside linkages are substrates for cellularRNase H. Since they are substrates, they activate the cleavage of targetRNA by RNase H. However, these authors furhter noted that in Xenopusembryos, both phosphodiester linkages and phosphororthioate linkages arealso subject to exonuclease degradation. Nuclease degraedation isdetrimental since it rapidly depletes the oligonucleotide.

[0007] As described in references (1), (2) and (4), to stabilizeoligonucleotides against nuclease degradation while still providing forRNase H activation, 2′-deoxy oligonucleotides having a short section ofphosphodiester linked nuclosides positioned between sections ofphosphoramidate, alkyl phosphonate or phosphotriester linkages wereconstructed. While the phosphoramidate-containing olignocleotides werestabilized against exonucleases, in reference (4) the authors notatedthat each phosphoramidate linkage resulted in a loss of 1.6° C. in themeasured T_(m) value of the phosphoramidate-containing oligonucleotides.Such a decrease in the T_(m) value is indicative of a decrease inhybridization between the oligonucleotide and its target strand.

[0008] Other authors have commented on the effect such a loss ofhybridization between an oligonucleotide and its target strand can have.Saison-Behmoaras et al. (EMBO Journal, 1991, 10, 1111) observed thateven though an oligonucleotide could be a substrate for Rnase H,cleavage efficiency by Rnase H was low because of weak hybridization tothe MRNA. The authors also noted that the inclusion of an acridinesubstitution at the 3′ end of the olignucleotide protected theoligonucleotide from exonucleases.

[0009] U.S. Pat. No. 5,013,830, issued May 7, 1991, discloses mixedoligomers comprising an RNA oligomer, or a derivative thereof,conjugated to the DNA oligomer via a phosphodiester linkage. The RNAoligomers also bear 2′-O-alkyl substituents. However, beingphosphodiesters, the oligomers are susceptible to nuclease cleavage.

[0010] European Patent applicatoin 339,842, published Nov. 2, 1989,disclosed 2″-O-substituted phosphorothioate oligonucleotides, including2′-O-methylribooligonucleotide phosphorothioate derivatives. Theabove-mentioned application also discloses 2′-O-methyl phosphodiesteroligonucleotides which lack nuclease resistance.

[0011] U.S. Pat. No. 5,149,797, issued Sep. 22, 1992, discloses mixedphosphate backbone oligonucleotides which include an internal portion ofdeoxynucleotides linked by phosphodiester linkages, and flanked on eachside by a portion of modified DNA or RNA sequences. The flankingsequences include methyl phosphonate, phosphoromorpholidate,phosphoropiperazidate or phosphoramidate linkages.

[0012] U.S. Pat. No. 5,256,775, issued Oct. 26, 1993, describes mixedoligonucleotides that incorporate phosphoramidate linkages andphosphorothioate or phosphorodithioate linkages.

[0013] U.S. Pat. No. 5,407,711, issued Apr. 4, 1995, describes RNA:DNAprobes targeted to DNA. The probes are labeled and are used in a systemthat includes RNase H. The RNase H enzyme cleaves those probes that bindto DNA targets. The probes can include modified phosphate groups.Mentioned are phosphotriester, hydrogen phosphonates, alkyl or arylphosphoates, alkyl or aryl phosphoramidates, phosphorothioates orphosphoroselenates.

[0014] In contrast to the pharmacological inhibition of gene expressionvia the RNase H enzyme, it is becoming clear that organisms frombacteria to humans use endogenous antisense RNA transcripts to alter thestability of some target mRNAS and regulate gene expression, see Nellen,W., and Lichtenstein, C., Curr.Opin.Cell.Biol., 1993, 18, 419-424 andNellen, W., et al, Biochem. Soc.Trans. 1992, 20, 750-754. Perhaps one ofthe best examples comes from certain bacteria where an antisense RNAregulates the expression of mok MRNA, which is required for thetranslation of the cytotoxic hok protein. Thus as the antisense leveldrops, mok mRNA levels and consequently hok protein levels rise and thecells die, see Gerdes, K. et al., J.Mol.Biol., 1992, 226, 637-649. Othersystems regulated by such mechanisms in bacteria include the RNA I-RNAII hybrid of the ColE1 plasmid, see Haeuptle, M. T., Frank, R., andDobberstein, B., Nucleic Acids Res. 1986, 14, 1427, Knecht, D., CellMotil.Cytoskel., 1989, 14, 92-102; and Maniak, M., and Nellen, W.,Nucleic Acids Res., 1990, 18, 5375-5380; OOP-cII RNA regulation inbacteriophage Lambda, see Krinke, L., and Wulff, D. L. (1990) GenesDev., 1990, 4, 2223-2233; and the copA-copT hybrids in E. coli. SeeBlomberg, P., Wagner, E. G., and Nordstrom, K., EMBO J., 1990, 9,2331-2340. In E. coli the RNA:RNA duplexes formed have been shown to besubstrates for regulated degradation by the endoribonuclease RNase III.Duplex dependent degradation has also been observed in thearchaebacterium, Halobacterium salinarium, where the antisensetranscript reduces expression of the early (T1) transcript of the phagegene phiH, see Stolt, P., and Zillig, W., Mol. Microbiol., 1993, 7,875-882. In several eukaryotic organisms endogenous antisensetranscripts have also been observed. These include p53, see Khochbin andLawrence, EMBO, 1989, 8, 4107-4114; basic fibroblast growth factor, seeVolk et al, EMBO, 1989, 8, 69, 2983-2988; N-myc, see Krystal, G. W.,Armstrong, B. C., and Battey, J. F., Mol. Cell. Biol., 1990, 10,4180-4191; eIF-2α, see Noguchi et al., J. Biol. Chem., 1994, 269,29161-29167. The conservation of endogenously expressed antisensetranscripts across evolutionary lines suggests that their biologicalroles and molecular mechanisms of action may be similar.

[0015] In bacteria, RNase III is the double stranded edoribonuclease(dsRNase) activity responsible for the degradation of someantisense:sense RNA duplexes. RNase III carries out site-specificcleavage of dsRNA-containing structures, see Saito, H. and Richardson,C. C., Cell, 1981, 27, 533-540. The RNase III also plays an importantrole in mRNA processing and in the processing of rRNA precursors into16S, 23S and 5S ribosomal RNAs, see Dunn, J. J. and Studier, F. W. J.Mol. Biol., 1975, 99, 487. In eukaryotes, a yeast gene (RNT1) hasrecently been cloned that codes for a protein that has homology to E.coli RNase III and shows dsRNase activity in ribosomal RNA processing,see Elela, S. A., Igel, H. and Ares, M. Cell, 1996, 85, 115-124. Aviancells treated with interferon produce and secrete a soluble nucleasecapable of degrading dsRNA, see Meegan, J. and Marcus, P. I., Science,1989, 244, 1089-1091. However such a secreted dsRNA activity is not alikely candidate to be involved in cytoplasmic degradation ofantisense:sense RNA duplexes. Despite these findings almost nothing isknown about human or mammalian dsRNAse activities. While it has beenrecognized that regulation (via any mechanism) of a target RNA strandwould be useful, to date only two mechanisms for eliciting such aneffect are known. These are hybridization arrest and use of anoligodeoxynucleotide to effect RNase H cleavage of the RNA target.Accordingly, there remains a continuing long-felt need for methods andcompounds for regulation of target RNA. Such regulation of target RNAwould be useful for therapeutic purposes both in vivo and ex vivo and,as well as, for diagnostic reagents and as research reagents includingreagents for the study of both cellular and in vitro events.

SUMMARY OF THE INVENTION

[0016] In accordance with this invention there are provided oligomericcompounds formed from a linear sequence of linked ribonucleosidesubunits that are specifically hybridizable to a preselected RNA target.The oligomeric compounds have at least a first segment and a secondsegment. The first segment incorporates at least one ribonucleosidesubunit that is modified to improve at least one of its pharmacokineticproperties, its binding characteristics to target RNA or to modify itscharge. The second segment includes at least four consecutiveribofuranosyl nucleoside subunits. The subunits of the oligomericcompounds are connected together in a linear sequence by internucleosidelinkages that are stabilized from degradation as compared tophosphodiester linkages.

[0017] In certain preferred embodiments of the invention, the compoundswill include a third segment having properties corresponding to theproperties of the first segment. It is preferred to position the secondsegment between the first and third segments such that they form acontinuous, linear sequences of linked nucleoside units. In preferredcompounds the number of such linked nucleoside subunits will range fromabout eight to about fifty with a more preferred range being fromabout-twelve to about thirty linked nucleoside subunits.

[0018] Modification of pharmacokinetic properties includes any one ormore of the modification of binding, absorption, distribution orclearance properties of the compound. Modification of bindingcharacteristics includes modification of the affinity or specificity ofsaid compound to its target RNA. Modification of the charge of saidcompound includes modifying the net charge of the compound as comparedto an unmodified compound. Normally modification of charge will decreasethe overall net negative charge of a phosphorus linked oligomericcompound to provide the compound with less negative charge, a neutralcharge or a net positive charge.

[0019] Further in accordance with this invention, there are providedoligomeric compounds formed from linear sequences of linkedribonucleoside subunits that are specifically hybridizable to apreselected RNA target. The oligomeric compounds have at least a firstsegment and a second segment. The first segment incorporates at leastone ribonucleoside subunit that is functionalized to provide greateraffinity to the target RNA. The second segment includes at least fourribofuranosyl nucleoside subunits. The subunits of the oligomericcompounds are connected together in a linear sequence by internucleosidelinkages that are modified to stabilize the linkages from degradation ascompared to phosphodiester linkages.

[0020] In certain preferred oligomeric compounds of the invention, thefirst or first and third segments of oligomeric compounds are formed ofnucleoside subunits that include 2′-substituent groups thereon. Inpreferred embodiments, the 2′-substituent group includes fluoro, C₁-C₂₀alkoxy, C₁-C₉ aminoalkoxy, allyloxy, imidazolylalkoxy and polyethyleneglycol. Preferred alkoxy substituents include methoxy, ethoxy andpropoxy. A preferred aminoalkoxy substituent is aminopropoxy. Apreferred imidazolylalkoxy substituent is imidazolylpropoxy. A preferredpolyethylene glycol substituent is —O-ethyl-O-methyl, i.e.,methoxyethoxy or —O—CH₂—CH₂—O—CH₃.

[0021] In further preferred oligomeric compounds of the invention, theoligomeric compounds are formed of nucleoside subunits that are modifiedby including certain selected nucleobases thereon. In preferredembodiments, the selected nucleobases include 2,6-diaminopurine,N2-alkylpurines, N2-aminoalkylpurines, 7-deaza-7-substituted purines,5-substituted pyrimidines, and 2-substituted pyrimidines.

[0022] Other preferred oligomeric compounds of the invention includeoligoribonucleotides having nucleoside subunits connected by phosphoruslinkages including phosphorothioate, 3′-(or −5′)deoxy-3′-(or −5′)thio-phosphorothioate, phosphoro-dithioate, phosphoroselenates, 3′-(or−5′)deoxy phosphinates, borano phosphates, 3′-(or −5′)deoxy-3′-(or5′-)amino phosphor-amidates, hydrogen phosphonates, borano phosphateesters, phosphoramidates, alkyl or aryl phosphonates andphospho-triester linkages. A selected group of oligoribonucleotidelinkages for use in linking the nucleosides of the second segmentinclude phosphorothioate, phosphinates and phosphor-amidates, all ofwhich are charged species.

[0023] Further preferred oligomeric compounds of the invention may alsoinclude oligoribonucleosides having nucleoside subunits connected bycarbonate, carbamate, silyl, sulfur, sulfonate, sulfonamide, formacetal,thioformacetal, oxime, methyleneimino, methylenemethylimino,methylenehydrazo, methylenedimethylhydrazo and methyleneoxymethyliminolinkages.

[0024] Further preferred oligomeric compounds of the invention includehaving nucleoside subunits connected by alternating phosphorus andnon-phosphorous linkages. Such non-phosphorous linkages includecarbonate, carbamate, silyl, sulfur, sulfonate, sulfonamide, formacetal,thioformacetal, oxime, methyleneimino, methylenemethylimino,methylenehydrazo, methylenedimethylhydrazo and methyleneoxymethyliminolinkages while the phosphorous linkages include phosphodiester,phosphorothioate, 3′-(or −5′)deoxy-3′-(or −5′)thio-phosphoro-thioate,phosphorodithioate, phosphoroselenates, 3′-(or −5′)deoxy phosphinates,borano phosphates, 3′-(or −5′) deoxy-3′-(or 5′-)amino phosphoramidates,hydrogen phosphonates, borano phosphate esters, phosphoramidates, alkylor aryl phosphonates and phosphotriester linkages.

[0025] Further preferred oligomeric compounds of the invention includeoligoribonucleotides, oligoribonucleosides or mixtures ofoligoribonucleotides and oligoribonucleosides having a plurality oflinked nucleoside subunits that are linked in a sequences that iscomplementary strand of target RNA and wherein the sequence of thecompound is divided into a first subsequence or segment and a secondsubsequence or segment. The first subsequence comprises linkednucleoside subunits bearing 2′-O-substituted-pentofuranosyl sugarmoieties and the second subsequence comprises linked nucleoside subunitsbearing 2′-hydroxyl-pentofuranosyl sugar moieties. Preferably, saidsecond subsequence has from four to twelve or more nucleoside subunits,and more preferably, has five to about nine nucleoside subunits. Infurther preferred embodiments there exists a third subsequence, thenucleoside subunits of which are selected from those which areselectable for the first subsequence. It is preferred that the secondsubsequence be positioned between the first and the third subsequences.Such oligomeric compounds of the invention are also referred to as“chimeras,” “chimeric” or “gapped” oligoribonucleotides oroligoribonucleosides.

[0026] In further preferred oligomeric compounds of the invention,nucleoside subunits bearing substituents that are modified to improve atleast one of: pharmacokinetic binding, absorption, distribution orclearance properties of the compound: affinity or specificity of saidcompound to said target RNA: or modification of the charge of saidcompound, compared to an unmodified compound;-are located at one or bothof the 3′ or the 5′ termini of the oligomeric compounds. In certainpreferred compounds there are from one to about eight nucleosidesubunits that are substituted with such substituent groups.

[0027] The nucleoside subunits are joined together in a linear sequenceto form the oligomeric compounds of the invention. Each nucleosidesubunit includes a base fragment and a sugar fragment. The base fragmentcomprises a heterocyclic base, alternately hereinafter referred to as anucleobase. The bases or nucleobases are covalently bonded to the sugarfragment. The sugar fragments may include a 2′-substituted sugar moiety,a 2′-hydroxyl sugar moiety or a sugar surrogate moiety.

[0028] Preferred nucleobases of the invention include purines andpyrimidines such as adenine, guanine, cytosine, uridine, and thymine, aswell as other synthetic and natural nucleobases such as xanthine,hypoxanthine, 2-aminoadenine, 6-methyl and other alkyl derivatives ofadenine and guanine, 2-propyl and other alkyl derivatives of adenine andguanine, 5-halouracil and cytosine, 5-propynyl uracil and cytosine,6-azo uracil, cytosine and thymine, 5-uracil (pseudouracil),4-thiouracil, 8-halo, amino, thiol, thioalkyl, hydroxyl and other8-substituted adenines and guanines, 5-trifluoromethyl and other5-substituted uracils and cytosines, and 7-methylguanine. Furtherpurines and pyrimidines include those disclosed in U.S. Pat. Nos.3,687,808, 5,484,908, 5,459,255, 5,457,191 and 5,614,617 (correspondingto U.S. patent application Ser. No. 07/971,978), and those disclosed inthe Concise Encyclopedia Of Polymer Science And Engineering, pages858-859, Kroschwitz, J. I., ed. John Wiley & Sons, 1990, and thosedisclosed by Englisch et al., Angewandte Chemie, International Edition,1991, 30, 613.

[0029] Preferred sugar fragments are pentoribofuranosyl sugar moieties,i.e, the “natural” sugar moiety of messenger ribonucleic acids. Othersugar-like or sugar surrogate compounds suitable for use in theoligoribonucleotides or oligoribonucleosides of the invention includecyclobutyl nucleoside surrogates as described in U.S. Pat. No.5,359,044, pyrrolidine nucleoside surrogates as described in U.S. Pat.No. 5,519,134, morpholino nucleoside surrogates as described in U.S.Pat. Nos. 5,142,047 and 5:235,033, and in related patent disclosures,and PNA (peptide nucleic acid) nucleoside surrogates.

[0030] In further preferred embodiments of the invention there areprovided synthetic oligomeric compounds that are specificallyhybridizable with a preselected RNA target and where the compoundsinclude a first segment including at least one surrogate nucleosidesubunit and a second segment comprising at least four ribofuranosylnucleoside subunits located. in a consecutive sequence and having2′-hydroxyl moieties thereon. Further the nucleoside subunits of theoligomeric compound are connected by internucleoside linkages that arestable to degradation as compared to phosphodiester bonds.

[0031] In other preferred embodiments of the invention, there areprovided synthetic oligomeric compounds that are specificallyhybridizable with a preselected RNA target and that include a firstsegment having at least one ribofuranosyl nucleoside subunit that is nota DNA or RNA “major” building block nucleoside and a second segment thatincludes at least four consecutive ribofuranosyl nucleoside subunitshaving 2′-hydroxyl moieties thereon. The nucleoside subunits of thecompounds are connected by internucleoside linkages which are modifiedto stabilize the linkages from degradation as compared to phosphodiesterlinkages. Nucleoside subunits that are not DNA or RNA major buildingblock nucleosides as that term is used in connection with thisinvention, are members of the group consisting of adenosine,2′-deoxyadenosine, guanosine, 2′-deoxyguanosine, cytidine,2′-deoxycytidine, uridine and 2′-deoxythymidine. As such, this groupexcludes “minor” nucleosides that may be found in tRNA or in othernucleic acids.

[0032] The invention also provides methods of for specifically cleavingpreselected RNA. These methods include contacting the RNA with acompound that includes at least twelve ribofuranosyl nucleosidessubunits joined in a sequence which is specifically hybridifzable withthe preselected RNA. The nucleoside subunits are joined byinternucleoside bonds that are stable to degradation as compared tophosphodiester bonds. The compound-has at least one segment thatincludes at least one modified nucleoside subunit, which modifiednucleoside subunit is modified to improve at least one ofpharmacokinetic binding, absorption, distribution or clearanceproperties of the compound; affinity or specificity of the compound totarget RNA; or modification of the charge of the compound, compared toan unmodified compound. The compound additionally includes a furthersegment having at least four ribonucleoside subunits.

[0033] The invention also provides methods for treating an organismhaving a disease characterized by the undesired production of a protein.These methods include contacting the organism with an oligomericcompound of the invention having a sequence of nucleoside subunitscapable of specifically hybridizing with a complementary strand ofribonucleic acid with at least one of the nucleoside subunits beingfunctionalized to modify one of more properties of the oligomericcompounds compared to native RNA. The compound further includes aplurality of the nucleoside subunits having 2′-hydroxyl-pentofuranosylsugar moieties.

[0034] Further in accordance with the present invention, there areprovided compositions including a pharmaceutically effective amount ofan oligomeric compound having a sequence of nucleoside subunits capableof specifically hybridizing with a complementary strand of RNA andwherein at least one of the nucleoside subunits is modified to improveat least one of pharmacokinetic binding, absorption, distribution orclearance properties of the compound; affinity or specificity of saidcompound to said target RNA; or modification of the charge of saidcompound, compared to an unmodified compound. In such compounds, aplurality of the nucleoside subunits have 2′-hydroxyl-pentofuranosylsugar moieties. The compositions further include a pharmaceuticallyacceptable diluent or carrier.

[0035] The present invention also provides mammalian ribonucleases,isolatable from human T24 cells, other cell lines, and rat tissues, thatdegrade RNA in an oligoribonucleotide:RNA duplex. Such a ribonuclease isreferred to herein as a dsRNase, wherein “ds” indicates the RNase'sspecificity for certain double-stranded RNA substrates. Usefulsubstrates for such dsRNases are also herein provided, as well asaffinity matrices comprising such substrates.

[0036] Methods are also provided for in vitro modification of asequence-specific target RNA including contacting a test solutioncontaining a dsRNase enzyme, i.e., a double stranded RNase enzyme, andsaid target RNA with an oligomeric compound. The oligomeric compound hasa sequence of nucleoside subunits capable of specifically hybridizing toa complementary strand of the nucleic acid, where at least one of thenucleoside subunits is functionalized to increase the binding affinityor binding specificity of the oligoribonucleotide to the complementarystrand of nucleic acid, and where a plurality of the nucleoside subunitshave 2′-hydroxyl-pentofuranosyl sugar moieties.

[0037] There are also provided methods of concurrently enhancinghybridization and/or dsRNase enzyme activation in an organism thatincludes contacting the organism with an oligomeric compound having asequence of nucleoside subunits capable of specifically hybridizing to acomplementary strand of target RNA. At least one of the nucleosidesubunits is modified to improve at least one of pharmacokinetic binding,absorption, distribution or clearance properties of the compound;affinity or specificity of said compound to said target RNA; ormodification of the charge of said compound, compared to an unmodifiedcompound. Again, a plurality of the nucleoside subunits have2′-hydroxy-pentofuranosyl sugar moieties.

[0038] The invention further provides diagnostic methods for detectingthe presence or absence of abnormal RNA molecules, or abnormal orinappropriate expression of normal RNA molecules in organisms or cells.The invention further provides research reagents for modulating enzymeactivity including dsRNase activity in in vitro solutions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]FIG. 1 schematically depicts certain illustrative chimericoligomeric compounds of the invention wherein open squares represent2′-methoxy modified ribonucleotides, filled circles represent2′-hydroxyl ribonucleotides and phosphorothioate linkages are utilizedthrough the compounds shown in the figure.

[0040] FIGS. 2 depicts Ha-ras mRNA levels in cells treated with full2′-methoxy or chimeric RNA gapmer oligonucleotides. Northern blotanalyses for Ha-ras mRNA levels in T24 cells treated with the indicateddoses of full 2′-methoxy oligonucleotide (panel 2A) or 3 gapoligoribonucleotide (panel 2C) for 24 hrs. are shown. The upper band isthe signal for Ha-ras, this signal was normalized to that obtained forG3PDH (lower band), relative Ha-ras levels were determined and arepresented graphically (panels 2C-2D). Neither oligonucleotide treatmentreduced Ha-ras mRNA levels.

[0041]FIG. 3 shows Northern blot analyses of T24 cell treated as in FIG.2 except with chimeric RNA gapmer oligonucleotides containing either a5, 7 or 9 ribonucleotide gap or a full ribonucleotide molecule (leftpanels 3A, 3B, 3C and 3D, respectively); cells were also treated with acontrol oligoribonucleotide that contains four mismatched base pairs tothe Ha-ras mRNA sequence (left panel 3E). Ha-ras signals were normalizedto that of G3PDH and relative Ha-ras levels are shown graphically (rightpanels).

[0042] In FIG. 4, the effect of T24 cytosolic extracts and RNase H onduplexes in vitro are shown. A 17 base pair duplex consisting of theHa-ras targeted 9 RNA gapmer oligonucleotide annealed to a ³²P-labeledRNA complement was incubated with 3 ug of T24 cytosolic protein fractionfor the indicated times at 37° C., the reaction was stopped and productswere resolved on a denaturing polacrylamide gel. Digestion products(arrows) indicate that cleavage of the duplex is restricted to theRNA:RNA region (see schematic of duplex, far right).

[0043]FIG. 5 shows the same 9 RNA gapmer oligonucleotide:RNA duplex asin FIG. 4, incubated with or without E. coli RNase H (− and +,respectively). The lack of digestion products indicates that this duplexis not a substrate for RNase H. Duplexes consisting of ³²p-labeled RNAannealed to either a full oligodeoxynucleotide (middle panel) or 9 DNAgapmer oligonucleotide (left panel) are substrates for cleavage. byRNase H and thus generate digestion products as expected (arrows).

[0044]FIG. 6 depicts SDS-polyacrylamide gel electrophoretic analysis ofthe concentrated rat liver active fractions after size exclusionchromatography. MW, molecular weight markers in kilodaltons (kD).Fraction 3 (lane 4), having an apparent molecular weight in the range ofabout 35 to about 100 kD, with much of the material having an apparentmolecular weight in the range 50 to about 80 kD, had the greatest amountof dsRNase activity.

[0045]FIG. 7 shows analysis of products of digestion of dsRNAsesubstrates by native polyacrylamide gel electrophoresis. Antisense andsense oligonucleotides were preannealed and incubated with cellularextracts and purified dsRNases as decribed herein. Lane 1, untreated“sense” strand 35 RNA; lane 2, “sense” strand RNA treated with 0.02units RNase V1; remaining lanes: dsRNAse substrates treated with 0.02(lane 3) and 0.002 (lane 4) units of RNase V1, with unpurified nuclearextract for 0 minutes (lane 5) or 240 minutes (lane 6), with unpurifiednuclear extract for 240 minutes without Mg** (lane 7), with unpurifiedcytosolic extract for 240 minutes (lane 8), with ion exchange purifiedcytosolic extract for 240 minutes in the presence (lane 9) or absence(lane 10) of Mg++, and with ion exchange/gel filtration purifiedcytosolic extract for 240 minutes in the presence (lane 9) or absence(lane 10) of Mg++.

[0046]FIG. 8 shows analysis of products of digestion of dsRNAsesubstrates by denaturing polyacrylamide gel electrophoresis. Lane 1,“sense” strand RNA treated with 5×10⁻³ units of RNase A; lane 2, “sense”strand RNA treated with 0.02 units RNase V1; lanes 3-9: dsRNAse productstreated with 0.02 (lane 3) and 0.002 (lane 4) units of RNase V1, withunpurified nuclear extract for 0 minutes (lane 5) or 240 minutes (lane6), with unpurified cytosolic extract for 240 minutes (lane 7), with ionexchange purified cytosolic extract for 240 minutes (lane 8), and withion exchange/gel filtration purified cytosolic extract for 240 minutes(lane 9). Lane 10, base hydrolysis ladder.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0047] While not wishing to be bound by theory, it is now believed thatby the use of certain chemically modified oligomeric compounds, one canexploit certain enzymatic activities in eukaryotic cells, includinghuman cells, resulting from the unexpected interaction of thesecompounds with a target RNA strand to form double-stranded RNA likestructures that are cleaved by certain enzymes. Heretofore, suchactivity has not recognized nor exploited in eukaryotic systems. It hasnow been found that the oligomeric compounds of the invention havecertain RNA like features that allow them to form a double strandedstructure with a targeted RNA region and this double stranded structureis subsequently degraded by eukaryotic dsRNases, i.e. double-strandedRNase enzymes, in a cell or test solution. Using T24 human bladdercarcinoma cells as an illustrative eukaryotic cellular system, it hasbeen demonstrated that this activity is present at comparable levels inboth the nuclear and cytoplasmic fractions.

[0048] In certain illustrative procedures provided herein to illustratethis invention, in common with some other known nuclease activities, ithas been found that this activity leaves 5′ phosphate and 3′ hydroxylgroups after cleavage of the RNA substrate. This generation of 5′phosphate, 3′ hydroxyl termini is a feature in common with several othernucleases that recognize double-stranded nucleic acid molecules,including RNase HI and II that cleave the RNA component of a DNA:RNAduplex in E.coli., RNase III which catalyses the hydrolysis of highmolecular weight double stranded RNA and mediates degradation ofsense-antisense duplexes, and RNase V1.

[0049] Many components of mRNA degradation systems have been conservedbetween prokaryotes and eukaryotes. It has now been found that likeprokaryotic organisms, in which RNase III carries out the degradation ofsense-antisense hybrids to regulate expression of some genes, humancells have conserved an activity capable of performing a similar role.In addition to other uses including therapeutic and diagnostic uses, byvirtue of this activity the compounds of this invention can be used asresearch reagents to assist in understanding how human cells useendogenously expressed antisense transcripts to modulate geneexpression.

[0050] The vast majority of antisense oligonucleotides usedexperimentally or currently being tested in the clinic in humans aremodified oligodeoxynucleotides. It has been demonstrated that theheteroduplex formed between such oligodeoxynucleotide antisensecompounds and their target RNA is recognized by an intracellularnuclease, RNase H, that cleaves only the RNA strand of this duplex.Although RNase H mediated degradation of target RNA has proven a usefulmechanism, it has certain limitations. RNase H is highly sensitive tostructural modifications made to the antisense oligonucleotides and thusmost of the modifications designed to improve the therapeutic propertiessuch as increased affinity, increased nuclease resistance and greatercellular permeability have resulted in oligonucleotides that do notsupport cleavage by RNase H. Another limitation to RNase H as aterminating mechanism of antisense action is the fact that theoligonucleotides must be DNA ‘like’, and in being DNA ‘like’, sucholigonucleotides have inherently low affinity to their target RNA.Strategies designed to circumvent this low affinity include the designof “gapmer” oligonucleotides that are composed of a stretch of highaffinity chemically modified oligonucleotides on the 5′ and 3′ ends (thewings) with a stretch of unmodified deoxyoliqonucleotides in the center(the gap). DNA gapmers, i.e., oligodeoxynucleotides gapmers, havesignificantly higher affinities for their target thanoligodeoxynucleotides, however, depending on the size of the DNA gap,RNase H activity has been shown to be compromised.

[0051] In using RNase H as a termination mechanism via RNA degradation,the cellular localization and tissue distribution of RNase H must alsobe considered. RNase H activity is primarily localized to the nucleusalthough it has been detected in the cytoplasm at lower levels. Most ofa given mRNA is found in the cytoplasm of cells, therefore the idealactivity to be exploited as a terminating mechanism would be one withhigh levels in both the nucleus and the cytoplasm. RNase H activity alsois highly variable from cell line to cell line or between tissues, thusa given disease state may not be a good candidate for RNA degradationonly because the target tissue has insufficient RNase H activity. It isclear that alternative terminating mechanisms for degrading target RNAare highly desirable.

[0052] Among other uses, the activity that has now been recognized cannow be exploited as an alternative terminating mechanism to RNase H forantisense therapeutics. It has been found that in using RNA-likeoligonucleotides that have high affinity for their target and thushigher potency than DNA-like oligonucleotides, activity can be expressedin human cells. The presence of the activity in both the cytoplasm andthe nucleus allows the compounds of the invention to be used to inhibitmany RNA processing events from nuclear pre-mRNA splicing and transportto degradation of mature transcript in the cytoplasm.

[0053] To illustrate this invention and to compare it to other knownantisense mechanisms, e.g. RNase H, the dsRNAse activity induced by thecompounds of the invention has been examined by targeting it to codon 12of Ha-ras. As described in U.S. Pat. No. 5,297,248, corresponding toSer. No. 08/297,248, and its related application InternationalPublication Number WO 92/22651, published Dec. 23, 1992, both commonlyassigned with this application, the entire contents of which are herein.iicorporated by reference, the ras oncogenes are members of a genefamily that encode related proteins that are localized to the inner faceof the plasma membrane and have been shown to be highly conserved at theamino acid level, to bind GTP with high affinity and specificity, and topossess GTPase activity. Although the cellular function of ras geneproducts is unknown, their biochemical properties, along with theirsignificant sequence homology with a class of signal-transducingproteins, known as GTP binding proteins, or G proteins, suggest that rasgene products play a fundamental role in basic cellular regulatoryfunctions related to the transduction of extracellular signals acrossplasma membranes.

[0054] Three ras genes, designated H-ras, K-ras, and N-ras, have beenidentified in the mammalian genome. Mammalian ras genes acquiretransformation-inducing properties by single point mutations withintheir coding sequences. Mutations in naturally occurring ras oncogeneshave been localized to codons 12, 13, and 61. The most commonly detectedactivating ras mutation found in human tumors is in codon 12 of theH-ras gene in which a base change from GGC to GTC results in aglycine-to-valine substitution in the GTPase regulatory domain of theras protein product. This single amino acid change is thought to abolishnormal control of ras protein function, thereby converting a normallyregulated cell protein to one that is continuously active. It isbelieved that such deregulation of normal ras protein function isresponsible for the transformation from normal to malignant growth.

[0055] While for illustrative purposes, the compounds of the inventionare targeted to ras RNA, it is of course recognized that a host of otherRNAs also are suitable as the target RNA. Thus the compounds of theinvention can be used to modulate the expression of any suitable targetRNA that is naturally present in cells or any target RNA in vitro.

[0056] The ras target site utilized for illustrative purposes is one themost RNase H sensitive oligonucleotide sites that has been identified inthe literature. The selective inhibition of mutated genes such as theras oncogene necessitates hybridization of a regulatory compound in thecoding region of the mRNA. This requires either a high affinityinteraction between such a compound and ras mRNA to prevent displacementof the compound by the polysome, or rapid degradation of the target mRNAby a given terminating mechanism. Again while not wishing to be bound bytheory, the RNA like compounds of the invention, have both inherentlyhigh affinity and are able to take advantage of the cellular dsRNaseactivity.

[0057] In accordance with the objects of this invention, noveloligomeric compounds that bind to a target RNA strand and that aresubstrates for dsRNase enzymes are provided. The oligomeric compounds ofthe invention include oligoribonucleotides, oligoribonucleosides andother oligomeric compounds having a linear sequence of linkedribonucleoside subunits incorporated therein. Such other oligomericcompounds will include chimeric structures formed between PNA (peptidenucleic acid) segments and linked ribonucleosides. Thus for the purposesof this specification, the term “oligomeric compound” is meant to beinclusive of the terms oligoribonucleotides and oligoribonucleosides,either used singly or in combination, as well as other oligomericcompounds including chimeric compounds formed between PNA segments (andother surrogate nucleoside components) and linked ribonucleosidesegments. As used in this specification and the claims attached hereto,in one sense the term oligomeric compound is used to representoligoribonucleotides, in a further sense to representoligoribonucleosides, in even a further sense to represent mixtures ofoligoribonucleotides and oligoribonucleosides and in other instances toindicated further chimeric compounds such as the above identified PNAchimeric compounds.

[0058] The oligoribonucleotides and oligoribonucleosides of theinvention are assembled from a plurality of nucleoside subunits. Incertain preferred oligoribonucleotide or oligoribonucleosides of theinvention at least one of the nucleoside subunits bear a substituentgroup that increases the binding affinity of the oligoribonucleotide oroligoribonucleoside for a complementary strand of nucleic acid.Additionally, at least some of the nucleoside subunits comprise2′-hydroxyl-pentofuranosyl sugar moieties.

[0059] For cellular use, for an oligonucleotide to be particularlyuseful, the oligonucleotide must be reasonably stable to nucleases inorder to survive in cells for a time period sufficient for it tointeract with target nucleic acids of the cells. Therefore, in certainembodiments of the invention, specific nucleoside subunits orinternucleoside linkages are functionalized or selected to increase thenuclease resistance of the oligoribonucleotide or oligoribonucleoside.However, for non-cellular uses, such as use of oligomeric compounds ofthe invention as research reagents and as diagnostic agents, suchnuclease stability may not be necessary.

[0060] In determining the extent of binding affinity of a first nucleicacid to a complementary nucleic acid, the relative ability of the firstnucleic acid to bind to the complementary nucleic acid may be comparedby determining the melting temperature of a particular hybridizationcomplex. The melting temperature (T_(m)) a characteristic physicalproperty of double stranded nucleotides, denotes the temperature (indegrees centigrade) at which 50% helical (hybridized) versus coil(unhybridized) forms are present. T_(m) is measured by using the UVspectrum to determine the formation and breakdown (melting) of thehybridization complex. Base stacking which occurs during hybridizationis accompanied by a reduction in UV absorption (hypochromicity).Consequently, a reduction in UV absorption indicates a higher T_(m). Thehigher the T_(m), the greater the strength of the bonds between thestrands.

[0061] It has been found in the present invention that the bindingaffinity of oligoribonucleotides and oligoribonucleosides of the presentinvention can be increased by incorporating substituent groups in thenucleoside subunits of these compounds. Preferred substituent groups are2′ substituent groups, i.e. substituent groups located at the 2′position of the pentofuranosyl sugar moieties of the nucleoside subunitsof the compounds of the present invention. Presently preferredsubstituent groups include fluoro, alkoxy, amino-alkoxy, allyloxy,imidazolylalkoxy and polyethylene glycol. Alkoxy and aminoalkoxy groupsgenerally include lower alkyl groups, particularly C₁-C₉ alkyl.Polyethylene glycols are of the structure (O—CH₂—CH₂)_(n)—O-alkyl. Aparticularly preferred substituent group is a polyethylene glycolsubstituent of the formula (—O—CH₂—CH₂)_(n)—O-alkyl, wherein n=1 andalkyl=CH₃. This modification has been shown to increase both affinity ofa oligonucleotide for its target and nuclease resistance of anoligonucleotide.

[0062] A further particularly useful 2′-substituent group for increasingthe binding affinity is the 2′-fluoro group. In a published study(Synthesis and Biophysical Studies of 2′-dRIBO-F ModifiedOligonucleotides, Conference On Nucleic Acid Therapeutics, Clearwater,FL, Jan. 13, 1991) an increase in binding affinity of 1.6° C. persubstituted nucleoside subunit was reported for a 15-mer phosphodiesteroligonucleotide having 2′-fluoro substituent groups on five of thenucleoside subunits of the oligonucleotide. When 11 of the nucleosidesubunits of the oligonucleotide bore 2′-fluoro substituent groups, thebinding affinity increased to 1.8° C. per substituted nucleosidesubunit. In this study, the 15-mer phosphodiester oligonucleotide wasderivatized to the corresponding phosphorothioate analog. When the15-mer phosphodiester oligonucleotide was compared to itsphosphorothioate analog, the phosphorothioate analog had a bindingaffinity of only about 66% of that of the 15-mer phosphodiesteroligonucleotide. Stated otherwise, binding affinity was lost inderivatizing the oligonucleotide to its phosphorothioate analog.However, when 2′-fluoro substituents were located on 11 of thenucleosides subunits of the 15-mer phosphorothioate oligonucleotide, thebinding affinity of the 2′-substituent groups more than overcame thedecrease noted by derivatizing the 15-mer oligonucleotide to itsphosphorothioate analog. In this compound, i.e. the 15-merphosphorothioate oligonucleotide having 11 nucleoside subunitssubstituted with 2′-fluoro substituent groups, the binding affinity wasincreased to 2.5° C. per substituent group.

[0063] For use in preparing the nucleoside structural subunits of thecompounds of the invention, suitable nucleobases for incorporation inthese nucleoside subunits include purines and pyrimidines such asadenine, guanine, cytosine, uridine, and thymine, as well as othersynthetic and natural nucleobases such as xanthine, hypoxanthine,2-aminoadenine, 6-methyl and other alkyl derivatives of adenine andguanine, 2-propyl and other alkyl derivatives of adenine and guanine,5-halouracil and cytosine, 5-propynyl uracil and cytosine, 6-azo uracil,cytosine and thymine, 5-uracil (pseudouracil), 4-thiouracil, 8-halo,amino, thiol, thioalkyl, hydroxyl and other 8-substituted adenines andguanines, 5-trifluoromethyl and other 5-substituted uracils andcytosines, 7-methylguanine. Further purines and pyrimidines includethose disclosed in U.S. Pat. No. 3,687,808, those disclosed in theConcise Encyclopedia Of Polymer Science And Engineering, pages 858-859,Kroschwitz, J. I., ed. John Wiley & Sons, 1990, and those disclosed byEnglisch et al., Angewandte Chemie, International Edition, 1991, 30,613. Certain of these nucleobases are particularly useful for increasingthe binding affinity of the oligomeric compounds of the invention. Theseinclude 5-substituted pyrimidines, 6-azapyrimidines and N-2, N-6 and O-6substituted purines, including 2-aminopropyladenine, 5-propynyluraciland 5-propynylcytosine. Other modified pyrimidine and purine bases arealso expected to increase the binding affinity of oligomeric compoundsto a complementary strand of nucleic acid.

[0064] Preferred oligoribonucleotides and oligoribonucleosides inaccordance with this invention preferably comprise from about 5 to about50 nucleoside subunits. In the context of this invention it isunderstood that this encompasses non-naturally occurring oligomers ashereinbefore described, having 5 to 50 nucleoside subunits.I It is morepreferred that the oligoribonucleotides and oligoribonucleosides of thepresent invention comprise from about 15 to about 25 nucleosidesubunits. As will be appreciated, a “nucleoside subunit” is a nucleobaseand sugar or sugar surrogate combination suitably bound to adjacentsubunits through phosphorus linkages in oligoribonucleotides and throughnon-phosphorus linkages in oligoribonucleosides. In this context, theterm “nucleoside subunit” is used interchangeably with the term“nucleoside unit” or “nucleoside.”

[0065] The oligoribonucleotides of the invention have their nucleosidesubunits connected by phosphorus linkages including phosphodiester,phosphorothioate, 3′-(or −5′)deoxy-3′-(or −5′)thio-phosphorothioate,phosphorodithioate, phosphoroselenates, 3′-(or −5′)deoxy phosphinates,borano phosphates, 3′-(or −5′)deoxy-3′-(or 5′-)amino phosphoramidates,hydrogen phosphonates, borano phosphate esters, phosphoramidates, alkylor aryl phosphonates and phosphotriester phosphorus linkages. Whereasthe oligoribonucleosides of the invention have their nucleoside subunitsconnected by carbonate, carbamate, silyl, sulfur, sulfonate,sulfonamide, formacetal, thioformacetyl, oxime, methyleneimino,methylenemethylimino, methylenehydrazo, methylenedimethylhydrazo andmethyleneoxymethylimino linkages.

[0066] In order to elicit a dsRNase response within the total overallsequence length of the oligomeric compounds of the invention there willbe a segment or subsequence of greater than three, but preferably, four,five or more consecutively linked 2′-hydroxyl-pentofuranosyl-containingnucleoside subunits. It is presently preferred to incorporate the2′-hydroxyl-pentofuranosyl-containing nucleoside subsequence in theoligomeric compound such that further subsequences or segments ofoligomeric compound are located on either side of the2′-hydroxyl-pentofuranosyl-containing nucleoside subsequence. In such aconstruction, the 2′-hydroxyl-pentofuranosyl containing nucleosidesubsequence is also referred to as the “central” or “gap” region orsegment and the other nucleoside subsequences or segments are referredto as “flanking” or “wing” regions or segments. Thus the “gap” region isflanked on either side by “wings.” Other constructions are alsopossible, including locating the 2′-hydroxylpentofuranosyl containingnucleoside subsequence at either the 3′ or the 5′ terminus of theoligomeric compound of the invention. These other constructions can beconsidered as “open” gapped structures, i.e., the gap region is open onthe end (either 3′ or 5′ end) of the oligomeric compound.

[0067] The oligoribonucleotides and oligoribonucleosides used inaccordance with this invention may be conveniently and routinely madethrough the well-known technique of solid phase synthesis, see forexample “Oligonucleotide synthesis, a practical approach”, Ed. M. J.Gait, IRL Press, 1984; “Oligonucleotides and Analogues, A PracticalApproach”, Ed. F. Eckstein, IRL Press, 1991 (especially Chapter 1,Modern machine-aided methods of oligodeoxyribonucleotide synthesis,Chapter 2, Oligoribonucleotide synthesis, Chapter 3,2′-O-Methyloligoribonucleotides: synthesis and applications, Chapter 4,Phosphorothioate oligonucleotides, Chapter 5, Synthesis ofoligonucleotide phosphorodithioates, Chapter 6, Synthesis ofoligo-2′-deoxyribonucleoside methylphosphonates, and. Chapter 7,Oligodeoxynucleotides containing modified bases. Other particularlyuseful synthetic procedures, reagents, blocking groups and reactionconditions are described in Martin, P., Helv. Chim. Acta, 1995, 78,486-504; Beaucage, S. L. and Iyer, R. P., Tetrahedron, 1992, 48,2223-2311 and Beaucage, S. L. and Iyer, R. P., Tetrahedron, 1993, 49,6123-6194, or references referred to therein.

[0068] Equipment for oligonucleotide and oligonucleoside synthesis issold by several vendors including Applied Biosystems. Various amiditereagents are also commercially available, including 2′-O-methyl amiditesand 2′-O-hydroxyl amidites. Any other means for such synthesis may alsobe employed. The actual synthesis of the oligonucleotides is well withinthe talents of those skilled in the art. It is also well known to usesimilar techniques to prepare other oligonucleotides such as thephosphorothioates and alkylated derivatives. It is also well known touse similar techniques and commercially available modified amidites andcontrolled-pore glass (CPG) products such as biotin, fluorescein,acridine or psoralen-modified amidites and/or CPG (available from GlenResearch, Sterling Va.) to synthesize fluorescently labeled,biotinylated or other conjugated oligonucleotides.

[0069] In a further embodiment, the present invention is drawn to amammalian ribonuclease isolatable from human T24 cells, and other celllines, that degrades RNA in an antisense oligoribonucleotide:RNA duplex.The ribonuclease is referred to herein as a dsRNase, wherein “ds”indicates the RNase's specificity for double-stranded RNA substrates.Antisense oligodeoxynucleotides containing 2′-methoxy modified sugarmoieties bind to their cellular mRNA targets with high affinity but theresulting [“DNA-like”]:[RNA] duplexes are not substrates for nucleolyticdegradation in T24 cells. As detailed in the Examples, 2′-methoxyphosphorothioate antisense oligonucleotides targeting codon 12 of Ha-RasmRNA were modified by substituting 2′-methoxy nucleotides with a stretchof ribonucleotides in the center of the oligonucleotide to form2′-methoxy/ribo/2′-methoxy chimeric or “gapmer” oligonucleotides, withthe phosphorothioate linkage maintained throughout the molecules. These“RNA-like” gapmer oligonucleotides bind to their cellular mRNA targetwith an affinity comparable to that of the full 2′-methoxyoligodeoxynucleotide, but, unlike the [“DNA-like”]:[RNA] duplexes, theresultant [“RNA-like”]:[RNA] duplexes are substrates for nucleolyticdegradation in T24 cells. Degradation of the [antisense “RNA-like”gapmer oligonucleotide]:[Ha-Ras mRNA] duplex is dependent on the numberof ribonucleotides incorporated into the antisense molecule. A 17 basepair 9 RNA gapmer oligonucleotide:RNA duplex is not a substrate forRNase H cleavage, but is a substrate for cleavage by an the dsRNase ofthe invention in T24 cellular lysates. Furthermore, the cleavage sitesseen with T24 cellular lysates are localized to the RNA:RNA portion ofthe duplex and are not seen in the 2′-methoxy:RNA portion of the duplex.Cleavage of the duplex by the dsRNase of the invention produces5′-phosphate and 3′-hydroxyl termini.

[0070] Compounds of the invention can be utilized as diagnostics,therapeutics and as research reagents and kits. They can be utilized inpharmaceutical compositions by adding an effective amount of a compoundof the invention to a suitable pharmaceutically acceptable diluent orcarrier. They further can be used for treating organisms having adisease characterized by the undesired production of a protein. Theorganism can be contacted with a compound of the invention having asequence that is capable of specifically hybridizing with a strand oftarget nucleic acid that codes for the undesirable protein.

[0071] The formulation of therapeutic compositions and their subsequentadministration is believed to be within the skill of those in the art.In general, for therapeutics, a patient in need of such therapy isadministered a compound in accordance with the invention, commonly in apharmaceutically acceptable carrier, in doses ranging from 0.01 μg to100 g per kg of body weight depending on the age of the patient and theseverity of the disease state being treated. Further, the treatmentregimen may last for a period of time which will vary depending upon thenature of the particular disease, its severity and the overall conditionof the patient, and may extend from once daily to once every 20 years.Following treatment, the patient is monitored for changes in his/hercondition and for alleviation of the symptoms of the disease state. Thedosage of the compound may either be increased in the event the patientdoes not respond significantly to current dosage levels, or the dose maybe decreased if an alleviation of the symptoms of the disease state isobserved, or if the disease state has been ablated.

[0072] In some cases it may be more effective to treat a patient with acompound of the invention in conjunction with other traditionaltherapeutic modalities. For example, a patient being treated for a viraldisease may be administered a compound of the invention in conjunctionwith a known antiviral agent, or a patient with atherosclerosis may betreated with a compound of the invention following angioplasty toprevent reocclusion of the treated arteries.

[0073] Following successful treatment, it may be desirable to have thepatient undergo maintenance therapy to prevent the recurrence of thedisease state, wherein the compound of the invention is administered inmaintenance doses, ranging from 0.01 μg to 100 g per kg of body weight,once or more daily, to once every 20 years.

[0074] The pharmaceutical compositions of the present invention may beadministered in a number of ways depending upon whether local orsystemic treatment is desired and upon the area to be treated.Administration may be topical (including ophthalmic, vaginal, rectal,intranasal, transdermal), oral or parenteral. Parenteral administrationincludes intravenous drip, subcutaneous, intraperitoneal orintramuscular injection, or intrathecal or intraventricularadministration.

[0075] Formulations for topical administration may include transdermalpatches, ointments, lotions, creams, gels, drops, suppositories, sprays,liquids and powders. Conventional pharmaceutical carriers, aqueous,powder or oily bases, thickeners and the like may be necessary ordesirable. Coated condoms, gloves and the like may also be useful.

[0076] Compositions for oral administration include powders or granules,suspensions or solutions in water or non-aqueous media, capsules,sachets or tablets. Thickeners, flavoring agents, diluents, emulsifiers,dispersing aids or binders may be desirable.

[0077] Compositions for intrathecal or intraventricular administrationmay include sterile aqueous solutions which may also contain buffers,diluents and other suitable additives.

[0078] Formulations for parenteral administration may include sterileaqueous solutions which may also contain buffers, diluents and othersuitable additives.

[0079] Dosing is dependent on severity and responsiveness of the diseasecondition to be treated, with the course of treatment lasting fromseveral days to several months, or until a cure is effected or adiminution of disease state is achieved. Optimal dosing schedules can becalculated from measurements of drug accumulation in the body of thepatient. Persons of ordinary skill can easily determine optimum dosages,dosing methodologies and repetition rates. Optimum dosages may varydepending on the relative potency of individual compounds, and cangenerally be estimated based on EC₅₀s found to be effective in in vitroand in vivo animal models. In general, dosage is from 0.01 μg to 100 gper kg of body weight, and may be given once or more daily, weekly,monthly or yearly, or even once every 2 to 20 years.

[0080] Such treatment can be practiced in a variety of organisms rangingfrom unicellular prokaryotic and eukaryotic organisms to multicellulareukaryotic organisms. Any organism that utilizes DNA-RNA transcriptionor RNA-protein translation as a fundamental part of its hereditary,metabolic or cellular machinery is susceptible to such diagnostic,therapeutic and/or prophylactic treatment. Seemingly diverse organismssuch as bacteria, yeast, protozoa, algae, plant and higher animal forms,including warm-blooded animals, can be treated in this manner. Further,since each of the cells of multicellular eukaryotes also includes bothDNA-RNA transcription and RNA-protein translation as an integral part oftheir cellular activity, such therapeutics and/or diagnostics can alsobe practiced on such cellular populations. Furthermore, many of theorganelles, e.g. mitochondria and chloroplasts, of eukaryotic cells alsoinclude transcription and translation mechanisms. As such, single cells,cellular populations or organelles also can be included within thedefinition of organisms that are capable of being treated with thetherapeutic or diagnostic compounds of the invention. As used herein,therapeutics is meant to include eradication of a disease state, killingof an organism, e.g. bacterial, protozoan or other infection, or controlof aberrant or undesirable cellular growth or expression.

[0081] In the context of this invention, “target RNA” shall mean any RNAthat can hybridize with a complementary nucleic acid like compound.Further in the context of this invention, “hybridization” shall meanhydrogen bonding, which may be Watson-Crick, Hoogsteen or reversedHoogsteen hydrogen bonding, between complementary nucleobases.“Complementary” as used herein, refers to the capacity for precisepairing between two nucleobases. For example, adenine and thymine arecomplementary nucleobases which pair through the formation of hydrogenbonds. “Complementary” and “specifically hybridizable,” as used herein,refer to precise pairing or sequence complementarity between a first anda second nucleic acid-like oligomers containing nucleoside subunits. Forexample, if a nucleobase at a certain position of the first nucleic acidis capable of hydrogen bonding with a nucleobase at the same position ofthe second nucleic acid, then the first nucleic acid and the secondnucleic acid are considered to be complementary to each other at thatposition. The first and second nucleic acids are complementary to eachother when a sufficient number of corresponding positions in eachmolecule are occupied by nucleobases which can hydrogen bond with eachother. Thus, “specifically hybridizable” and “complementary” are termswhich are used to indicate a sufficient degree of complementarity suchthat stable and specific binding occurs between a compound of theinvention and a target RNA molecule. It is understood that an oligomericcompound of the invention need not be 100% complementary to its targetRNA sequence to be specifically hybridizable. An oligomeric compound isspecifically hybridizable when binding of the oligomeric compound to thetarget RNA molecule interferes with the normal function of the targetRNA to cause a loss of utility, and there is a sufficient degree ofcomplementarity to avoid non-specific binding of the oligomeric compoundto non-target sequences under conditions in which specific binding isdesired, i.e. under physiological conditions in the case of in vivoassays or therapeutic treatment, or in the case of in vitro assays,under conditions in which the assays are performed.

[0082] The following examples and procedures illustrate the presentinvention andzare not intended to limit the same. In illustrating theinvention, Example 1 identifies certain commercial nucleoside amiditesand other additional nucleoside amidites that are useful for thepreparation of certain illustrative oligoribonucleotide oroligoribonucleoside compounds of the invention. Examples 2 through 5illustrate the preparation of further nucleoside amidites use inpreparing other illustrative oligoribonucleotide or oligoribonucleosidecompounds of the invention. Example 6 illustrates the preparation ofoligoribonucleotide compounds of the invention. Example 7 illustratesthe preparation of oligoribonucleoside compounds of the invention.Examples 8 through 16 illustrate the preparation of chimeric oligomericcompounds of the invention including certain “gapmers,” i.e., compoundshaving “gap” and “wing” constructions. Examples 17 through 18 illustratecertain useful aspects of the compounds of the invention. Examples 19through 28 illustrate the identification, characterization andpurification of the double-stranded ribonucleases (dsRNases) of theinvention. Example 29 illustrates affinity columns incorporating thedsRNase substrates of the invention.

[0083] In the illustrative examples, several different types of“gapmers” are exemplified. These include a first type wherein the “gap”segment of linked nucleosides is positioned between 5′ and 3′ “wing”segments of linked nucleosides and a second “open end” type wherein the“gap” segment is located at either the 3′ or the 5′ terminus of theoligomeric compound. In the illustrative examples, for all chimericoligoribonucleotides and oligoribonucleosides, unless otherwiseindicated, 2′-O-methyl nucleosides are utilized in the “wing” segmentsand 2′-OH nucleosides are utilized in the “gap” segments of therespective oligoribonucleotides or oligoribonucleosides.

[0084] For the purposes of the illustrative examples the following shorthand conventions are used. Structure set forth in brackets, i.e. [ ],are nucleoside abbreviations, while structures set forth following aslash mark, i.e. /, are linkers used to connect the nucleosides, i.e.backbone structures that link the nucleosides together in eitheroligoribonucleotide or oligoribonucleoside compounds.

[0085] Using this nomenclature, the following abbreviations are used forphosphate linkages between nucleosides: PO for phosphodiester; PS forphosphorothioate, P2S for phosphorodithioate, PSe forphosphoroselenates, PMe for methyl phosphonate, POMe for methylphosphotriester, PN for phosphoramidate, 3′NPN for 3′-deoxy-3′-aminophosphoramidate, PI for phosphinate, MePS for alkylphosphonothioate, BPfor borano phosphate are used. For non-phosphate linkages betweennucleosides the abbreviations used are: MMI for methylenemethylimino,MDH for methylenedimethylhydrazo, FA for formacetal, TFA forthioformacetal, ETO for ethylene oxide and amide-3 formethylenecarbonylamino. 2′-OH is utilized as an abbreviation forunmodified ribo sugars, i.e. pentoribofuranosyl sugars. For modifiednucleosides the abbreviations used are: 2′-O-alkyl for general alkylgroups at the 2′ position of a pentoribofuranosyl moiety with specificalkyl being noted as 2′-O-Me, 2′-O-Et, 2′-O—Pr and 2′-O-EtOMe formethyl, ethyl, propyl and methoxyethyl, respectively; 2′-F for a fluoromoiety at the 2′ position of a pentoribofuranosyl moiety, Mod-Purine fora purine nucleobase substitution as, for example, per the disclosure ofU.S. Pat. No. 5,459,255 or; and Mod-Pyr for a pyrimidine nucleobasesubstitution as, for example, per the disclosure of U.S. Pat. No.5,484,908; SS for a sugar surrogate as, for example, per the disclosureof U.S. Pat. No. 5,359,044.

EXAMPLE 1

[0086] Amidites for Oligonucleotide/Oligonucleoside Synthesis

[0087] 2′-O-Methyl nucleoside amidites and 2′-OH (blocked as2′-t-butyldimethylsilyl derivative) nucleoside amidites are availablefrom Glen Research, Sterling, Va. Other 2′-O-alkyl subsituted nucleosideamidites are prepared as is described in U.S. Pat. Nos. 5,506,351,5,466,786 or 5,514,786, herein incorporated by reference. Cyclobutylsugar surrogate compounds are prepared as is described in U.S. Pat. No.5,359,044, herein incorporated by reference. Pyrrolidine sugar surrogateare prepared as is described in U.S. Pat. No. 5,519,134, hereinincorporated by reference. Morpholino sugar surrogates are prepared asis described in U.S. Pat. Nos. 5,142,047 and 5,235,033, hereinincorporated by reference, and other related patent disclosures. N-2substitued purine nucleoside amidites are prepared as is described inU.S. Pat. No. 5,459,255, herein incorporated by reference. 3-Deazapurine nucleoside amidites are prepared as is described in U.S. Pat. No.5,457,191, herein incorporated by reference. 5,6-Substituted pyrimidinenucleoside amidites are prepared as is decribed in U.S. Pat. No.5,614,617 herein incorporated by reference. 5-Propynyl pyrimidinenucleoside amidites are prepared as is described in U.S. Pat. No.5,484,908, herein incorporated by reference.

EXAMPLE 2

[0088] 2′-O-(Methoxyethyl) Nucleoside Amidites

[0089] 2′-O-Ethyl-O-methyl substituted nucleoside amidites are preparedas follows in Examples 2-a through 2-h or alternately, as per themethods of Martin, P., Helvetica Chimica Acta, 1995, 78, 486-504.

EXAMPLE 2-a

[0090] 2,2′-Anhydro[1-(β-D-arabinofuranosyl)-5-methyluridine]

[0091] 5-Methyluridine (ribosylthymine, commercially available throughYamasa, Choshi, Japan) (72.0 g, 0.279 M), diphenylcarbonate (90.0 g,0.420 M) and sodium bicarbonate (2.0 g, 0.024 M) were added to DMF (300mL). The mixture was heated to reflux, with stirring, allowing theevolved carbon dioxide gas to be released in a controlled manner. After1 hour, the slightly darkened solution was concentrated under reducedpressure. The resulting syrup was poured into diethylether (2.5 L), withstirring. The product formed a gum. The ether was decanted and theresidue was dissolved in a minimum amount of methanol (ca. 400 mL). Thesolution was poured into fresh ether (2.5 L) to yield a stiff gum. Theether was decanted and the gum was dried in a vacuum oven (60° C. at 1mm Hg for 24 h) to give a solid which was crushed to a light tan powder(57 g, 85% crude yield). The NMR spectrum was consistent with thestructure, contaminated with phenol as its sodium salt (ca. 5%). Thematerial was used as is for further reactions (or it can be purifiedfurther by column chromatography using a gradient of methanol in ethylacetate (10-25%) to give a white solid, mp 222-4° C.).

EXAMPLE 2-b

[0092] 2′-O-Methoxyethyl-5-methyluridine

[0093] 2,2′-Anhydro-5-methyluridine (195 g, 0.81 M),tris(2-methoxyethyl)borate (231 g, 0.98 M) and 2-methoxyethanol (1.2 L)were added to a 2 L stainless steel pressure vessel and placed in apre-heated oil bath at 160° C. After heating for 48 hours at 155-160°C., the vessel was opened and the solution evaporated to dryness andtriturated with MeOH (200 mL). The residue was suspended in hot acetone(1 L). The insoluble salts were filtered, washed with acetone (150 mL)and the filtrate evaporated. The residue (280 g) was dissolved in CH₃CN(600 mL) and evaporated. A silica gel column (3 kg) was packed inCH₂Cl₂/acetone/MeOH (20:5:3) containing 0.5% Et₃NH. The residue wasdissolved in CH₂Cl₂ (250 mL) and adsorbed onto silica (150 g) prior toloading onto the column. The product was eluted with the packing solventto give 160 g (63%) of product. Additional material was obtained byreworking impure fractions.

EXAMPLE 2-c

[0094] 2′-O-Methoxyethyl-5′-O-dimethoxytrityl-5-methyluridine

[0095] 2′-O-Methoxyethyl-5-methyluridine (160 g, 0.506 M) wasco-evaporated with pyridine (250 mL) and the dried residue dissolved inpyridine (1.3 L). A first aliquot of dimethoxytrityl chloride (94.3 g,0.278 M) was added and the mixture stirred at room temperature for onehour. A second aliquot of dimethoxytrityl chloride (94.3 g, 0.278 M) wasadded and the reaction stirred for an additional one hour. Methanol (170mL) was then added to stop the reaction. HPLC showed the presence ofapproximately 70% product. The solvent was evaporated and trituratedwith CH₃CN (200 mL). The residue was dissolved in CHCl₃ (1.5 L) andextracted with 2×500 mL of saturated NaHCO₃ and 2×500 mL of saturatedNaCl. The organic phase was dried over Na₂SO₄, filtered and evaporated.275 g of residue was obtained. The residue was purified on a 3.5 kgsilica gel column, packed and eluted with EtOAc/Hexane/Acetone (5:5:1)containing 0.5% Et₃NH. The pure fractions were evaporated to give 164 gof product. Approximately 20 g additional was obtained from the impurefractions to give a total yield of 183 g (57%).

EXAMPLE 2-d

[0096]3′-O-Acetyl-2′-O-methoxyethyl-5′-O-dimethoxytrityl-5-methyluridine

[0097] 2′-O-Methoxyethyl-5′-O-dimethoxytrityl-5-methyluridine (106 g,0.167 M), DMF/pyridine (750 mL of a 3:1 mixture prepared from 562 mL ofDMF and 188 mL of pyridine) and acetic anhydride (24.38 mL, 0.258 M)were combined and stirred at room temperature for 24 hours. The reactionwas monitored by tlc by first quenching the tlc sample with the additionof MeOH. Upon completion of the reaction, as judged by tlc, MeOH (50 mL)was added and the mixture evaporated at 35° C. The residue was dissolvedin CHCl₃ (800 mL) and extracted with 2×200 mL of saturated sodiumbicarbonate and 2×200 mL of saturated NaCl. The water layers were backextracted with 200 mL of CHCl₃. The combined organics were dried withsodium sulfate and evaporate to give 122 g of residue (approx. 90%product). The residue was purified on a 3.5 kg silica gel column andeluted using EtOAc/Hexane(4:1). Pure product fractions were evaporatedto yield 96 g (84%). An additional 1.5 g was recovered from laterfractions.

EXAMPLE 2-e

[0098]3′-O-Acetyl-2′-O-methoxyethyl-5′-O-dimethoxytrityl-5-methyl-4-triazoleuridine

[0099] A first solution was prepared by dissolving3′-O-acetyl-2′-O-methoxyethyl-5′-O-dimethoxytrityl-5-methyluridine (96g, 0.144 M) in CH₃CN (700 mL) and set aside. Triethylamine (189 mL, 1.44M) was added to a solution of triazole (90 g, 1.3 M) in CH₃CN (1 L),cooled to −5° C. and stirred for 0.5 h using an overhead stirrer. POCl₃was added dropwise, over a 30 minute period, to the stirred solutionmaintained at 0-10° C., and the resulting mixture stirred for anadditional 2 hours. The first solution was added dropwise, over a 45minute period, to the later solution. The resulting reaction mixture wasstored overnight in a cold room. Salts were filtered from the reactionmixture and the solution was evaporated. The residue was dissolved inEtOAc (1 L) and the insoluble solids were removed by filtration. Thefiltrate was washed with 1×300 mL of NaHCO₃ and 2×300 mL of saturatedNaCl, dried over sodium sulfate and evaporated. The residue wastriturated with EtOAc to give the title compound.

EXAMPLE 2-f

[0100] 2′-O-Methoxyethyl-5′-O-dimethoxytrityl-5-methylcytidine

[0101] A solution of3′-O-acetyl-2′-O-methoxyethyl-5′-O-dimethoxytrityl-5-methyl-4-triazoleuridine(103 g, 0.141 M) in dioxane (500 mL) and NH₄OH (30 mL) was stirred atroom temperature for 2 hours. The dioxane solution was evaporated andthe residue azeotroped with MeOH (2×200 mL). The residue was dissolvedin MeOH (300 mL) and transferred to a 2 liter stainless steel pressurevessel. MeOH (400 mL) saturated with NH₃ gas was added and the vesselheated to 100° C. for 2 hours (tlc showed complete conversion) . Thevessel contents were evaporated to dryness and the residue was dissolvedin EtOAc (500 mL) and washed once with saturated NaCl (200 mL). Theorganics were dried over sodium sulfate and the solvent was evaporatedto give 85 g (95%) of the title compound.

EXAMPLE 2-g

[0102]N⁴-Benzoyl-2′-O-methoxyethyl-5′-O-dimethoxytrityl-5-methylcytidine

[0103] 2′-O-Methoxyethyl-5′-O-dimethoxytrityl-5-methylcytidine (85 g,0.134 M) was dissolved in DMF (800 mL) and benzoic anhydride (37.2 g,0.165 M) was added with stirring. After stirring for 3 hours, tlc showedthe reaction to be approximately 95% complete. The solvent wasevaporated and the residue azeotroped with MeOH (200 mL). The residuewas dissolved in CHCl₃ (700 mL) and extracted with saturated NaHCO₃(2×300 mL) and saturated NaCl (2×300 mL), dried over MgSO₄ andevaporated to give a residue (96 g). The residue was chromatographed ona 1.5 kg silica column using EtOAc/Hexane (1:1) containing 0.5% Et₃NH asthe eluting solvent. The pure product fractions were evaporated to give90 g (90%) of the title compound.

EXAMPLE 2-h

[0104]N⁴-Benzoyl-2′-O-methoxyethyl-5′-O-dimethoxytrityl-5-methylcytidine-3′-amidite

[0105]N⁴-Benzoyl-2′-O-methoxyethyl-5′-O-dimethoxytrityl-5-methylcytidine (74g, 0.10 M) was dissolved in CH₂Cl₂ (1 L). Tetrazole diisopropylamine(7.1 g) and 2-cyanoethoxy-tetra-(isopropyl)phosphite (40.5 mL, 0.123 M)were added with stirring, under a nitrogen atmosphere. The resultingmixture was stirred for 20 hours at room temperature (tlc showed thereaction to be 95% complete). The reaction mixture was extracted withsaturated NaHCO₃ (1×300 mL) and saturated NaCl (3×300 mL). The aqueouswashes were back-extracted with CH₂Cl₂ (300 mL), and the extracts werecombined, dried over MgSO₄ and concentrated. The residue obtained waschromatographed on a 1.5 kg silica column using EtOAcHexane (3:1) as theeluting solvent. The pure fractions were combined to give 90.6 g (87%)of the title compound.

EXAMPLE 3

[0106] Preparation of Long Chain, i.e. (C₂₀), Substituted NucleosideAmidites

[0107] Synthesis of nucleoside amidites having long chains, e.g. C₂₀,substituents at their 2′ position is shown in Examples 3-a through 3-c.

EXAMPLE 3-a

[0108] Synthesis of2,6-Diamino-9-(2-O-octadecyl-β-D-ribofuranosyl)purine

[0109] 2,6-Diamino-9-(β-D-ribofuranosyl)purine (50 g, 180 mmol) andsodium hydride (7 g) in DMF (1 L) were heated to boiling for 2 hr.Iodooctadecane (100 g) was added at 150° C. and the reaction mixtureallowed to cool to RT. The reaction mixture was stirred for 11 days atRT. The solvent was evaporated and the residue purified by silica gelchromatography. The product was eluted with 5% MeOH/CH₂Cl₂. Theappropriate fractions were evaporated to yield the product (11 g). ¹HNMR (DMSO-d₆) δ0.84 (t, 3, CH₂); 1.22 (m, 32, O—CH₂—CH₂—(CH₂)₁₆); 1.86(m, 2, O—CH₂CH₂); 3.25 (m, 2, O—CH₂); 3.93 (d, 1, 4′H) , 4.25 (m, 1,3′H) ; 4.38 (t, 1, 2′H) ; 5.08 (d, 1, 3′-OH); 5.48 (t, 1, 5′-OH); 5.75(s, 2, 6-NH₂); 5.84 (d, 1, 1′-H); 6.8 (s, 2, 2-NH₂); and 7.95 (s, 1,8-H).

EXAMPLE 3-b

[0110] Synthesis of 2′-O-octadecylguanosine

[0111] 2,6-Diamino-9-(2-O-octadecyl-β-D-ribofuranosyl) purine (10 g) in0.1 M sodium phosphate buffer (50 mL, pH 7.4), 0.1 M tris buffer (1000mL, pH 7.4) and DMSO (1000 mL) was treated with adenosine deaminase (1.5g) at RT. At day 3, day 5 and day 7 an additional aliquot (500 mg, 880mg and 200 mg, respectively) of adenosine deaminase was added. Thereaction was stirred for a total of 9 day and purification by silica gelchromatography yielded the product (2 g). An analytical sample wasrecrystallized from MeOH ¹H NMR (DMSO-d₆) δ0.84 (t, 3, CH₃), 1.22 [s,32, O—CH₂—CH₂—(CH₂)₁₆], 5.07 (m, 2, 3′-OH and 5′-OH); 5.78 (d, 1, 1′-H);6.43 (s, 2, NH₂), 7.97 (s, 1, 8-H) and 10.64 (s, 1, NH₂). Anal. Calcd.for C₂₈H₄₉N₅O₅: C, 62.80; H, 9.16; N, 12.95. Found: C, 62.54; H, 9.18;N, 12.95.

EXAMPLE 3-c

[0112] Synthesis of N²-Isobutyryl-2′-O-octadecylguanosine

[0113] 2′-O-Octadecylguanosine (1.9 g) in pyridine (150 mL) was cooledin an ice bath, and treated with trimethylsilyl chloride (2 g, 5 eq) andisobutyryl chloride (2 g, 5 eq). The reaction mixture was stirred for 4hours, during which time it was allowed to warm to room temperature. Thesolution was cooled, water added (10 mL) and stirred for an additional30 minutes. Concentrated ammonium hydroxide (10 mL) was added and thesolution concentrated in vacuo. The residue was purified by silica gelchromatography (eluted with 3% MeOH/EtOAc) to yield 1.2 g of product. ¹HNMR (DMSO-d₆) δ0.85 (t, 3, CH₃), 1.15 (m, 38, O—CH₂CH₂(CH₂)₁₆,CH(CH₃)₂), 2.77 (m, 1, CH(CH₃)₂), 4.25 (m, 2, 2′-H and 3′-H); 5.08 (t,1, 5′-OH), 5.12 (d, 1, 3′-OH), 5.87 (d, 1, 1′-H), 8.27 (s, 1, 8-H),11.68 (s, 1, NH₂) and 12.08 (s, 1, NH₂). Anal. Calcd. for C₃₂H₅₅N₅O₆: C,63.47; H, 9.09; N, 11.57. Found: C, 63.53; H, 9.20; N, 11.52. Prior toincorporating this product into an oligonucleotide, it was converted toN²-Isobutyryl-5′-dimethoxytrityl-2′-O-octadecyl-guanosine and then to aphosphoramidite according to the procedures described in InternationalPublication Number WO 94/02501, published Feb. 3, 1994.

EXAMPLE 4

[0114] 2′-Fluoro Nucleoside Amidites

[0115] 2′-fluoro substituted nucleoside amidites are repared as followsin Examples 4-a through 4-d or alternately as per the method of Kawasakiet. al., J. Med. Chem., 1993, 36, 831-841.

EXAMPLE 4-a

[0116] i. N⁶-Benzoyl-9-β-D-arabinofuranosyladenine.

[0117] 9-β-D-arabinofuranosyladenine (1.07 g, 4.00 mmol) was dissolvedin anhydrous pyridine (20 mL) and anhydrous dimethylformamide (20 mL)under an argon atmosphere. The solution was cooled to 0° C. andchlorotrimethylsilane (3.88 mL, 30.6 mmol) was added slowly to thereaction mixture via a syringe. After stirring the reaction mixture at0° C. for 30 minutes, benzoyl chloride (2.32 mL, 20 mmol) was addedslowly. The reaction mixture was allowed to warm to 20° C. and stirredfor 2 hours. After cooling the reaction mixture to 0° C., cold water (8mL) was added and the mixture was stirred for 15 minutes. Concentratedammonium hydroxide (8 mL) was slowly added to the reaction mixture togive a final concentration of 2 M of ammonia. After stirring the coldreaction mixture for 30 minutes, the solvent was evaporated in vacuo (60torr) at 20° C. followed by evaporation in vacuo (1 torr) at 40° C. togive an oil. This oil was triturated with diethyl ether (50 mL) to givea solid which was filtered and washed with diethyl ether three times.This crude solid was triturated in methanol (100 mL) at refluxtemperature three times and the solvent was evaporated to yieldN⁶-Benzoyl-9-β-D-arabino- furanosyladenine as a solid (1.50 g, 100%).

[0118] ii. N⁶-Benzoyl-9- [3′, 5′-di-O-tetrahydropyran-2-yl)-β-D-arabinofuranosyl] adenine.

[0119] N⁶-Benzoyl-9-β-D-arabinofuranosyladenine (2.62 g, 7.06 mmol) wasdissolved in anhydrous dimethylformamide (150 mL) under argon andp-toluenesulfonic acid monohydrate (1.32 g, 6.92 mmol) was added. Thissolution was cooled to 0° C. and dihydropyran (1.26 mL, 13.8 mmol) wasadded via a syringe. The reaction mixture was allowed to warm to 20° C.Over a period of 5 hours a total of 10 equivalents of dihydropyran wereadded in 2 equivalent amounts in the fashion described. The reactionmixture was cooled to 0° C. and saturated aqueous sodium bicarbonate wasadded slowly to a pH of 8, then water was added to a volume of 750 mL.The aqueous mixture was extracted with methylene chloride (4×200 mL),and the organic phases were combined and dried over magnesium sulfate.The solids were filtered and the solvent was evaporated in vacuo (60torr) at 30° C. to give a small volume of liquid which was evaporated invacuo (1 torr) at 40° C. to give an oil. This oil was coevaporated withp-xylene in vacuo at 40° C. to give an oil which was dissolved inmethylene chloride (100 mL). Hexane (200 mL) was added to the solutionand the lower-boiling solvent was evaporated in vacuo at 30° C. to leavea white solid suspended in hexane. This solid was filtered and washedwith hexane (3×10 mL) then purified by column chromatography usingsilica gel and methylene chloride-methanol (93:7) as the eluent. Thefirst fraction yielded the title compound 3 as a white foam (3.19 g,83%) and a second fraction gave a white foam (0.81 g) which wascharacterized as the 5 -monotetrahydropyranyl derivative ofN⁶-Benzoyl-9-β-D-arabinofuranosyladenine.

[0120] iii.N⁶-Benzoyl-9-[2′-O-trifluoromethylsulfonyl-3′,5′-di-O-tetrahydropyran-2-yl)-β-D-arabinofuranosyl]adenine.

[0121] N⁶-Benzoyl-9-[3′, 5′-di-O-tetrahydropyran-2-yl)-β-D-arabinofuranosyl]adenine (2.65 g, 4.91 mmol) was dissolved inanhydrous pyridine (20 mL) and the solvent was evaporated in vacuo (1 mmHg) at 40° C. The resulting oil was dissolved in anhydrous methylenechloride (130 mL) under argon anhydrous pyridine (3.34 mL, 41.3 mmol)and N,N-dimethylaminopyridine (1.95 g, 16.0 mmol) were added. Thereaction mixture was cooled to 0° C. and trifluoromethanesulfonicanhydride (1.36 mL, 8.05 mmol) was added slowly via a syringe. Afterstirring the reaction mixture at 0° C. for 1 hour, it was poured intocold saturated aqueous sodium bicarbonate (140 mL). The mixture wasshaken and the organic phase was separated and kept at 0° C. The aqueousphase was extracted with methylene chloride (2×140 mL). The organicextracts which were diligently kept cold were combined and dried overmagnesium sulfate. The solvent was evaporated in vacuo (60 torr) at 20°C. then evaporated in vacuo (1 torr) at 20° C. to giveN⁶-Benzoyl-9-[2′-O-tri-fluoromethylsulfonyl-3′, 5′-di-O-tetrahydropyran-2-yl)-β-D- arabinofuranosyl]adenine as a crude oilwhich was not purified further.

[0122] iv. N⁶-Benzoyl-9-[2′-fluoro-3′,5′-di-O-tetrahydropyran-2-yl)-β-D-arabinofuranosyl] adenine.,

[0123] N⁶-Benzoyl-9-[2′-O-trifluoromethylsulfonyl-3 ′,5′-di-O-tetrahydropyran-2-yl)-β-D-arabinofuranosyl]adenine (4.9 mmol) asa crude oil was dissolved in anhydrous tetrahydrofuran (120 mL) and thissolution was cooled to 0° C. under argon. Tetrabutylammonium fluoride asthe hydrate (12.8 g, 49.1 mmol) was dissolved in anhydroustetrahydrofuran (50 mL) and half of this volume was slowly added via asyringe to the cold reaction mixture. After stirring at 0° C. for 1hour, the remainder of the reagent was added slowly. The reactionmixture was stirred at 0° C. for an additional 1 hour, then the solventwas evaporated in vacuo (60 torr) at 20° C. to give an oil. This oil wasdissolved in methylene chloride (250 mL) and washed with brine threetimes. The organic phase was separated and dried over magnesium sulfate.The solids were filtered and the solvent was evaporated to give an oil.The crude product was purified by column chromatography using silica gelin a sintered-glass funnel and ethyl acetate was used as the eluent.N⁶-Benzoyl-9-[2′-fluoro-3′,5′-di-O-tetrahydropyran-2-yl)-β-D-arabinofuranosyl]adenine was obtainedas an oil (2.03 g, 76%).

[0124] v. N6-Benzoyl-9-(2′-fluoro-β-D-ribofuranosyl) adenine.

[0125] N⁶-Benzoyl-9-[2′-fluoro-3′,5-′di-O-tetrahydropyran-2-yl)-β-D-arabinofuranosyl]adenine (1.31 g, 2.42mmol) was dissolved in methanol (60 mL), and Dowex 50W×2-100 (4 cm³, 2.4m.eq) was added to the reaction mixture. The reaction mixture wasstirred at 20° C. for 1 hour then cooled to 0° C. Triethylamine (5 mL)was then slowly added to the cold reaction mixture to a pH of 12. Theresin was filtered and washed with 30% triethylamine in methanol untilthe wash no longer contained UV absorbing material. Toluene (50 mL) wasadded to the washes and the solvent was evaporated at 24° C. in vacuo(60 torr, then 1 torr) to give a residue. This residue was partiallydissolved in methylene chloride (30 mL) and the solvent was transferredto a separatory funnel. The remainder of the residue was dissolved inhot (60° C.) water and after cooling the solvent it was also added tothe separatory funnel. The biphasic system was extracted, and theorganic phase was separated and extracted with water (3×100 mL). Thecombined aqueous extracts were evaporated in vacuo (60 torr, then 1 torrHg) at 40° C. to give an oil which was evaporated with anhydrouspyridine (50 mL). This oil was further dried in vacuo (1 torr Hg) at 20°C. in the presence of phosphorous pentoxide overnight to giveN⁶-benzoyl-9-(2′-fluoro-b-D-ribofuranosyl)adenine as a yellow foam (1.08g, 100%) which contained minor impurities.

[0126] vi.N⁶-Benzoyl-9-[2′-fluoro-5′-O-(4,4′-dimethoxy-trityl)-β-D-ribofuranosyl]adenine.

[0127] N⁶-Benzoyl-9-(2′-fluoro-β-D-ribofuranosyl)adenine (1.08 g, 2.89mmol) which contained minor impurities was dissolved in anhydrouspyridine (20 mL) under argon and dry triethylamine (0.52 mL, 3.76 mmol)was added followed by addition of 4,4′-dimethoxytrityl chloride (1.13 g,3.32 mmol). After 4 hours of stirring at 20° C. the reaction mixture wastransferred to a separatory funnel and diethyl ether (40 mL) was addedto give a white suspension. This mixture was washed with water threetimes (3×10 mL), the organic phase was separated and dried overmagnesium sulfate. Triethylamine (1 mL) was added to the solution andthe solvent was evaporated in vacuo (60 torr Hg) at 20° C. to give anoil which was evaporated with toluene (20 mL) containing triethylamine(1 mL). This crude product was purified by column chromatography usingsilica gel and ethyl acetate-triethylamine (99:1) followed by ethylacetate-methanol-triethylamine (80:19:1) to give the product in twofractions. The fractions were evaporated in vacuo (60 torr, then 1 torrHg) at 20° C. to give a foam which was further dried in vacuo (1 torrHg) at 20° C. in the presence of sodium hydroxide to giveN⁶-Benzoyl-9-[2′-fluoro-5′-O-(4,4′-dimethoxytrityl)-β-D-ribofuranosyl]adenineas a foam (1.02 g, 52%)

[0128] vii. N⁶-Benzoyl-[2′-fluoro-5′-O-(4,4′-dimethoxytrityl)]-adenosine-3′-O-N,N-diisopropyl-β-cyanoethyl phosphoramidite.

[0129]N⁶-Benzoyl-9-[2′-fluoro-5′-O-(4,4′-dimethoxytrityl)-β-D-ribofuranosyl]adenine(1.26 g, 1.89 mmol) was dissolved in anhydrous dichloromethane (13 mL)under argon, diisopropylethylamine (0.82 mL, 4.66 mmol) was added, andthe reaction mixture was cooled to 0° C.Chloro(diisopropylamino)-β-cyanoethoxyphosphine (0.88 mL, 4.03 mmol) wasadded to the reaction mixture which was allowed to warm to 20° C. andstirred for 3 hours. Ethylacetate (80 mL) and triethylamine (1 mL) wereadded and this solution was washed with brine (3×25 mL). The organicphase was separated and dried over magnesium sulfate. After filtrationof the solids the solvent was evaporated in vacuo at 20° C. to give anoil which was purified by column chromatography using silica gel andhexanes-ethyl acetate-triethyl-amine (50:49:1) as the eluent.Evaporation of the fractions in vacuo at 20° C. gave a foam which wasevaporated with anhydrous pyridine (20 mL) in vacuo (1 torr) at 26° C.and further dried in vacuo (1 torr Hg) at 20° C. in the presence ofsodium hydroxide for 24 h to giveN⁶-Benzoyl-[2′-deoxy-2′-fluoro-5′-O-(4,4′-dimethoxytrityl)]-adenosine-3′-O-(N,N-diisopropyl-β-cyanoethylphosphoramiditeas a foam (1.05 g, 63%).

EXAMPLE 4-b

[0130]2′-Deoxy-2′-fluoro-5′-O-(4,4′-dimethoxytrityl)-uridine3′O(N,N-diisopropyl-β-cyanoethyl-phosphoramidite).

[0131] 2,2′-Cyclouridine is treated with a solution of 70% hydrogenfluoride/pyridine in dioxane at 120° C. for ten hours to provide aftersolvent removal a 75% yield of 2′-deoxy-2′-fluorouridine. The 5′-DMT and3′-cyanoethoxydiisopropyl-phosphoramidite derivitized nucleoside isobtained by standard literature procedures [Gait, Ed., OligonucleotideSynthesis. A Practical Approach, IRL Press, Washington, D.C. (1984)], oraccording to the procedure of Example 4-a.

EXAMPLE 4-c

[0132]2′-Deoxy-2′-fluoro-5′-O-(4,4′-dimethoxytrityl)-cytidine-3′-O-(N,N-diisopropyl-β-cyanoethylphosphoramidite).

[0133] 2′-Deoxy-2′-fluorouridine (2.51 g, 10.3 mmol) was converted tocorresponding cytidine analog via the method of C. B. Reese, et al., J.Chem. Soc. Perkin Trans I, pp. 1171-1176 (1982), by acetylation withacetic anhydride (3.1 mL, 32.7 mmol) in anhydrous pyridine (26 mL) atroom temperature. The reaction was quenched with methanol, the solventwas evaporated in vacuo (1 torr) to give an oil which was coevaporatedwith ethanol and toluene. 3′, 5′-O-diacetyl-2′-deoxy-2′-fluoro-uridinewas crystallized from ethanol to afford colorless crystals (2.38 g,81%).

[0134] N-4-(1,2,4-triazol-1-yl)-3′,5′-O-diacetyl-2′-deoxy-2′-fluorouridine was obtained in a 70% yield(2.37 g) by reaction of 3′, 5′-O-diacetyl-2′-deoxy-2′-fluorouridine(2.75 g, 9.61 mmol) with 1,2,4-triazole (5.97 g, 86.5 mmol), phosphorusoxychloride (1.73 mL, 18.4 mmol), and triethylamine (11.5 mL, 82.7 mmol)in anhydrous acetonitrile at room temperature. After 90 min the reactionmixture was cooled to ice temperature and triethylamine (7.98 ml, 56.9mmol) was added followed by addition of water (4.0 ml). The solvent wasevaporated in vacuo (1 torr) to give an oil which was dissolved inmethylene chloride and washed with saturated aqueous sodium bicarbonate.The aqueous phase was extracted with methylene chloride twice (2×100 mL)and the organic extracts dried with magnesium sulfate. Evaporation ofthe solvent afforded an oil from which the productN-4-(1,2,4-triazol-1-yl)-3′, 5′-O-diacetyl-2′-deoxy-2′-fluorouridine wasobtained by crystallization from ethanol.

[0135] 2′-deoxy-2′-fluorocytidine was afforded by treatment of protectedtriazol-1-yl derivative with concentrated ammonium hydroxide (4.26 mL,81.2 mmol) in dioxane at room temperature for 6 hours. After evaporationof the solvent the oil was stirred in half-saturated (at icetemperature) ammonia in methanol for 16 hours. The solvent wasevaporated and 2′-deoxy-2′-fluoro-cytidine crystallized fromethyl-acetate-methanol (v/v, 75:25) to give colorless crystals (1.24 g,75%).

[0136] N-4-benzoyl-2′-deoxy-2′-fluorocytidine was prepared by selectivebenzoylation with benzoic anhydride in anhydrous dimethylformamide, V.Bhat, et al. Nucleosides Nucleotides, Vol. 8, pp. 179-183 (1989). The5′-O-(4,4′-dimethoxytrityl)-3′-O-(N,N-diisopropyl-β-cyanoethyl-phosphoramidite)was prepared in accordance with Example 4-a.

EXAMPLE 4-d

[0137] i. 9-(3′,5′-[1,1,3,3-Tetraisopropyldisilox-1,3-diyl]-β-D-arabinofuranosyl)guanine.

[0138] The 3′ and 5′ positions of guanosine were protected by theaddition of a TPDS (1,1,3,3-tetraisopropyldisilox-1,3-diyl) protectinggroup as per the procedure of Robins et al. [Can. J. Chem., 61, 1911(1983)]. To a stirred solution of DMSO (160 mL) and acetic anhydride (20mL) was added the TPDS guanosine (21 g, 0.040 mol). The reaction wasstirred at room temperature for 36 hours and then cooled to 0° C. Coldethanol (400 mL, 95%) was added and the reaction mixture further cooledto −78° C. in a dry ice/acetone bath. NaBH₄ (2.0 g, 1.32 mol. eq.) wasadded. The reaction mixture was allowed to warm up to −2° C., stirredfor 30 minutes and again cooled to −78° C. This was repeated twice.After the addition of NaBH₄ was complete, the reaction was stirred at 0°C. for 30 minutes and then at room temperature for 1 hour. The reactionwas taken up in ethyl acetate (1 L) and washed twice with a saturatedsolution of NaCl. The organic layer was dried over MgSO₄ and evaporatedunder reduced pressure. The residue was coevaporated twice with tolueneand purified by silica gel chromatography using CH₂Cl₂-MeOH (9:1) as theeluent. Pure product (6.02 g) precipitated from the appropriate columnfractions during evaporation of these fractions, and an additional 11.49g of product was obtained as a residue upon evaporation of thefractions.

[0139] ii. N²-Isobutyryl-9-(2′-O-isobutyryl-3′,5′-[1,1,3,3-tetraiso-propyldisilox-1,3-diyl]-β-D-arabinofuranosyl)guanine.

[0140] 9-(3′,5′-[1,1,3,3-Tetraisopropyldisilox-1,3-diyl]-β-D-arabinofuranosyl)guanine(6.5 g, 0.01248 mol) was dissolved in anhydrous pyridine (156 mL)-underargon. DMAP (9.15 g) was added. Isobutyric anhydride (6.12 mL) wasslowly added and the reaction mixture stirred at room temperatureovernight. The reaction mixture was poured into cold saturated NaHCO₃(156 mL) and stirred for 10 minutes. The aqueous solution was extractedthree times with ethyl acetate (156 mL). The organic phase was washedthree times with saturated NaHCO₃ and evaporated to dryness. The residuewas coevaporated with toluene and purified by silica gel columnchromatography using CH₂Cl₂-acetone (85:15) to yield 5.67 g of product.

[0141] iii.N²-Isobutyryl-9-(2′-O-isobutyryl-β-D-arabinofuranosyl)-guanine.

[0142]N²-Isobutyryl-9-(2′-isobutyryl-3′,5′-[1,1,3,3-tetra-isopropyldisilox-1,3-diyl]-β-D-arabinofuranosyl)guanine(9.83 g, 0.01476 mol) was dissolved in anhydrous THF (87.4 mL) at roomtemperature under argon. 1 M (nBu)₄N⁺F⁻ in THF (29.52 mL, 2 eq.) wasadded and the reaction mixture stirred for 30 minutes. The reactionmixture was evaporated at room temperature and the residue purified bysilica gel column chromatography using EtOAc-MeOH (85:15) to yield 4.98g (80%) of product.

[0143] iv.N²-Isobutyryl-9-(2′-O-isobutyryl-3′,5′-di-O-[tetrahydro-pyran-2-yl]-β-D-arabinofuranosyl)guanine.

[0144] N²-Isobutyryl-9-(2′-isobutyryl-β-D-arabinofuranosyl)-guanine (4.9g) was dissolved in anhydrous 1,4-dioxane (98 mL) at room temperatureunder argon. p-Toluenesulphonic acid monohydrate (0.97 g) was addedfollowed by 3,4-dihydro-2H-pyran (DHP, 9.34 mL, 8.8 eq.). The reactionmixture was stirred for 2 hours, then cooled to 0° C. and saturatedNaHCO₃ (125 mL) was added to quench the reaction. The reaction mixturewas extracted three times with 125 mL portions of CH₂Cl₂ and the organicphase dried over MgSO₄. The organic phase was evaporated and the residuedissolved in minimum volume of CH₂Cl₂, but in an amount sufficient toyield a clear liquid not a syrup, and then dripped into hexane (100times the volume of CH₂Cl₂). The precipitate was filtered to yield 5.59(81.5%) of product.

[0145] v.N²-Isobutyryl-9-(3′,5′-di-O-[tetrahydropyran-2-yl]-β-D-arabinofuranosyl)guanine.

[0146]N²-Isobutyryl-9-(2′-isobutyryl-3′,5′-di-O-[tetra-hydropyran-2-yl]-β-D-arabinofuranosyl)guanine(5.58 g) was dissolved in pyridine-MeOH—H₂O (65:30:15, 52 mL) at roomtemperature. The solution was cooled to 0° C. and 52 mL of 2 N NaOH inEtOH-MeOH (95:5) was added slowly, followed by stirring for 2 hours at0° C. Glacial acetic acid was added to pH 6, and saturated NaHCO₃ wasadded to pH 7. The reaction mixture was evaporated under reducedpressure and the residue coevaporated with toluene. The residue was thendissolved in EtOAc (150 mL) and washed 3× with saturated NaHCO₃. Theorganic phase was evaporated and the residue purified by silica gelcolumn chromatography using EtOAc-MeOH (95:5) as the eluent, yielding3.85 g (78.3%) of product.

[0147] vi.N²-Isobutyryl-9-(3′,5′-di-O-[tetrahydropyran-2-yl]-2′-O-trifluoromethylsulfonyl-β-D-arabinofuranosyl)guanine.

[0148]N²-Isobutyryl-9-(3′,5′-di-O-[tetrahydropyran-2-yl]-β-D-arabinofuranosyl)guanine(3.84 g) was dissolved in anhydrous CH₂Cl₂ (79 mL), anhydrous pyridine(5 mL) and DMAP (2.93 g) at room temperature under argon. The solutionwas cooled to 0° C. and trifluoromethanesulfonic anhydride (1.99 mL) wasslowly added with stirring. The reaction mixture was stirred at roomtemperature for 1 hour then poured into 100 mL of saturated NaHCO₃. Theaqueous phase was extracted three times with cold CH₂Cl₂. The organicphase was dried over MgSO₄, evaporated and coevaporated with anhydrousMeCN to yield a crude product.

[0149] vii.N²-Isobutyryl-9-(2′-deoxy-2′-fluoro-3′,5′-di-O-[tetra-hydropyran-2-yl]-2′-O-trifluoromethylsulfonyl-β-D-ribofurano-syl)guanine.

[0150] CrudeN²-isobutyryl-9-(3′,5′-di-O-[tetrahydropyran-2-yl]-2′-O-trifluoromethylsulfonyl-β-D-arabinofuranosyl)guaninewas dissolved in anhydrous THF (113 mL) under argon at 0° C. 1 M(nBu)₄N⁺F⁻(dried by coevaporation with pyridine) in THF (36.95 mL) wasadded with stirring. After 1 hour, a further aliquot of (nBu)₄N⁺F⁻ inTHF (36.95 mL) was added. The reaction mixture was stirred at 0° C. for5 hours and stored overnight at −30° C. The reaction mixture wasevaporated under reduced pressure and the residue dissolved in CH₂Cl₂(160 mL) and extracted five times with deionized water. The organicphase was dried over MgSO₄ and evaporated. The residue was purified bysilica gel column chromatography using EtOAc-MeOH (95:5) to yield 5.25 gof product.

[0151] viii.N²-Isobutyryl-9-(2′-deoxy-2′-fluoro-β-D-ribofuranosyl)-guanine.

[0152]N²-isobutyryl-9-(2′-deoxy-2′-fluoro-3′,5′-di-O-[tetrahydropyran-2-yl]-β-D-ribofuranosyl)guanine(3.85 g) was dissolved in MeOH (80 mL) at room temperature. Pre-washedDowex 50W resin (12.32 cm³) was added and the reaction mixture stirredat room temperature for 1 hour. The resin was filtered and the filtrateevaporated to dryness. The resin was washed withpyridine-triethylamine-H₂O (1:3:3) until filtrate was clear. Thisfiltrate was evaporated to obtain an oil. The residues from bothfiltrates were combined in H₂O (200 mL) and washed with CH₂Cl₂ (3×100mL). The aqueous phase was evaporated to dryness and the residuerecrystallized from hot MeOH to yield 0.299 g of product as a whitepowder. The remaining MeOH solution was purified by silica gel columnchromatography to further yield 0.783 g of product by elution withEtOH-MeOH (4:1).

[0153] ix.N²-Isobutyryl-9-(2′-deoxy-2′-fluoro-5′-O-[4,4-dimethoxy-trityl]-β-D-ribofuranosyl)guanine.

[0154] N²-isobutyryl-9-(2′-deoxy-2′-fluoro-β-D-ribo-furanosyl)guanine(1.09 g) was dissolved in pyridine (20 mL) and triethylamine (0.56 mL)at room temperature under argon. 4,4′-Dimethoxytrityl chloride (1.20 g,1.15 molar eq.) was added and the reaction mixture stirred at roomtemperature for 5 hours. The mixture was transferred to a separatoryfunnel and extracted with diethyl ether (100 mL). The organic phase waswashed with saturated NaHCO₃ (3×70 mL), and the aqueous phaseback-extracted three times with diethyl ether. The combined organicphases were dried over MgSO₄ and triethylamine (4 mL) was added tomaintain the solution at basic pH. The solvent was evaporated and theresidue purified by silica gel column chromatography usingEtOAc-triethylamine (100:1) and then EtOAc-MeOH-triethylamine (95:5:1)as eluents yielding 1.03 g of product.

[0155] x.N²-Isobutyryl-9-(2′-deoxy-2′-fluoro-5′-O-[4,4-dimethoxy-trityl]-guanosine-3′-O-N,N-diisopropyl-β-D-cyanoethylphosphor-amidite.

[0156]N²-isobutyryl-9-(2′-deoxy-2′-fluoro-5′-O-[4,4′-dimethoxytrityl])-β-D-ribofuranosyl)guanine(0.587 g) was dissolved in anhydrous CH₂Cl₂ (31 mL) anddiisopropylethylamine (0.4 mL) at room temperature under argon. Thesolution was cooled to 0° C. andchloro(diisopropylamino)-β-cyanoethoxy-phosphine (0.42 mL) was slowlyadded. The reaction mixture was allowed to warm to room temperature andstirred for 3.5 hours. CH₂Cl₂-triethylamine (100:1, 35 mL) was added andthe mixture washed with saturated NaHCO₃ (6 mL). The organic phase wasdried over MgSO₄ and evaporated under reduced pressure. The residue waspurified by silica gel column chromatography usinghexane-EtOAc-triethylamine (75:25:1) for 2 column volumes, thenhexane-EtOAc-triethylamine (25:75:1), and finally EtOAc-triethylamine.The product-containing fractions were pooled and the solvent evaporatedunder reduced pressure. The resulting oil was coevaporated twice withMeCN and dried under reduced pressure. The resulting white solid wasdissolved in CH₂Cl₂ (3 mL) and dripped into stirring hexane (300 mL).The resulting precipitate was filtered and dried under reduced pressureto yield 0.673 g (88%) of product.

EXAMPLE 5

[0157] Nucleoside amidites having substitution on their sugar and theirbase fragments are shown in Examples 5-a through 5-k.

EXAMPLE 5-a

[0158] Other Nucleoside Amidites

[0159] i. 1-(2-Fluoro-β-D-erythro-pentofuranosyl)-5-methyluridine2,2′-Anhydro-[1-(β-D-arabinofuranosyl)-5-methyluridine] (71 g, 0.32mmol) (from Example 2-a) and dioxane (700 mL) are placed in a 2 literstainless steel bomb and HF/pyridine (100 g, 70%) was added. The mixturewas heated for 16 hours at 120-125° C. and then cooled in an ice bath.The bomb was opened and the mixture was poured onto 3 liters of ice. Tothis mixture was added cautiously sodium hydrogen carbonate (300 g) andsaturated sodium bicarbonate solution (400 mL). The mixture was filteredand the filter cake was washed with water (2×100 mL) and methanol (2×500mL). The water and methanol washes were concentrated to dryness invacuo. Methanol (200 mL) and coarse silica gel (80 g) were added to theresidue and the mixture was concentrated to dryness in vacuo. Theresulting material was concentrated onto the silica gel and purified bysilica gel column chromatography using a gradient of ethyl acetate andmethanol (100:0 to 85:15). Pooling and concentration of the productfractions gave 36.9 g (51%, 2 step yield) of the title compound.

[0160] Also isolated from this reaction was1-(2-phenyl-β-D-erythro-pentofuranosyl)-5-methyluridine (10.3 g). Thismaterial is formed from the phenol and its sodium salt from the anhydroreaction above when the bomb reaction is carried out on impure material.When The anhydro material is purified this product is not formed. Theformed 1-(2-phenyl-β-D-erythro-pentofuranosyl)-5-methyluridine wasconverted into its DMT/phosphoramidite using the same reactionconditions as for the 2′-Fluoro material.

[0161] ii.1-(5-O-Dimethoxytrityl-2-fluoro-β-D-erythro-pento-furanosyl)-5-methyluridine

[0162] 1-(2-fluoro-β-D-erythro-pentofuranosyl)-5-methyl-uridine (31.15g, 0.12 mol) was suspended in pyridine (150 mL) and dimethoxytritylchloride (44.62 g, 0.12 mol) was added. The mixture was stirred in aclosed flask for 2 hours and then methanol (30 mL) was added. Themixture was concentrated in vacuo and the resulting residue waspartitioned between saturated bicarbonate solution (500 mL) and ethylacetate (3×500 ml). The ethyl acetate fractions were pooled and driedover magnesium sulfate, filtered and concentrated in vacuo to a thickoil. The oil was dissolved in dichloromethane (100 mL), applied to asilica gel column and eluted with ethyl acetate:hexane:triethylamine,60/39/1 increasing to 75/24/1. The product fractions were pooled andconcentrated in vacuo to give 59.9 g (89%) of the title compound as afoam.

[0163] iii.1-(5-O-Dimethoxytrityl-2-fluoro-3-O-N,N-diisopropylamino-2-cyanoethylphosphite-β-D-erythro-pentofuranosyl)-5-methyluridine

[0164]1-(5-O-Dimethoxytrityl-2-fluoro-β-D-erythro-pento-furanosyl)-5-methyluridine(59.8 g, 0.106 mol) was dissolved in dichloromethane and 2-cyanoethylN,N,N′,N′-tetraisopropyl-phosphorodiamidite (46.9 mL, 0.148 mol) anddiisopropylamine tetrazolide (5.46 g, 0.3 eq.) was added. The mixturewas stirred for 16 hours. The mixture was washed with saturated sodiumbicarbonate (1 L) and the bicarbonate solution was back extracted-withdichloromethane (500 mL). The combined organic layers were washed withbrine (1 L) and the brine was back extracted with dichloromethane (100mL). The combined organic layers were dried over sodium sulfate,filtered, and concentrated to a vol of about 200 mL. The resultingmaterial was purified by silica gel column chromatography usinghexane/ethyl acetate/triethyl amine 60/40/1. The product fractions wereconcentrated in vacuo, dissolved in acetonitrile (500 ml), filtered,concentrated in vacuo, and dried to a foam. The foam was chopped anddried for 24 hour to a constant weight to give 68.2 g (84%) of the titlecompound. 1H NMR: (CDCl₃) δ0.9-1.4 (m, 14 H, 4×CH₃, 2×CH), 2.3-2.4 (t, 1H, CH₂CN), 2.6-2.7 (t, 1 H, CH2CN), 3.3-3.8 (m, 13 H, 2×CH₃OAr, 5′ CH₂,CH₂OP, C-5 CH₃), 4.2-4.3 (m, 1 H, 4′); 4.35-5.0 (m, 1 H, 3′), 4.9-5.2(m, 1 H, 2′), 6.0-6.1 (dd, 1 H, 1′), 6.8-7.4 (m, 13 H, DMT), 7.5-7.6 (d,1 H, C-6), 8.8 (bs, 1 H, NH). ³¹p NMR (CDCl₃); 151.468, 151.609,151.790, 151.904.

[0165] iv.1-(3′,5′-di-O-acetyl-2-fluoro-β-D-erythro-pentofuranosyl)-5-methyluridine

[0166] 1-(2-fluoro-β-D-erythro-pentofuranosyl)-5-methyl-uridine (22.4 g,92 mmol, 85% purity), prepared as per the procedure of Example 5-a-i.,was azeotroped with pyridine (2×150 mL) and dissolved in pyridine (250mL). Acetic anhydride (55 mL, 0.58 mol) was added and the mixture wasstirred for 16 hours. Methanol (50 mL) was added and stirring wascontinued for 30 minutes. The mixture was evaporated to a syrup. Thesyrup was dissolved in a minimum amount of methanol and loaded onto asilica gel column. Hexane/ethyl acetate, 1:1, was used to elute theproduct fractions. Purification gave 19.0 g (74%) of the title compound.

EXAMPLE 5-b

[0167] i.4-Triazine-1-(3′,5′-di-O-acetyl-2-fluoro-β-D-erythro-pentofuranosyl)-5-methyluridine

[0168] 1,2,4-Triazole (106 g, 1.53 mol) was dissolved in acetonitrile(150 mL) followed by triethylamine (257 mL, 1.84 mol). The mixture wascooled to between 0 and 10° C. using an ice bath. POCl₃ (34.5 mL, 0.375mol) was added slowly via addition funnel and the mixture was stirredfor an additional 45 minutes. In a separate flask,1-(3′,5′-Di-O-acetyl-2-fluoro-β-D-erythro-pentofuranosyl)-5-methyluridine(56.9 g, 0.144 mol) was dissolved in acetonitrile (150 mL). The solutioncontaining the1-(3′,5′-Di-O-acetyl-2-fluoro-β-D-erythro-pentofuranosyl)-5-methyluridinewas added via cannula to the triazole solution slowly. The ice bath wasremoved and the reaction mixture was allowed to warm to room temperaturefor 1 hour. The acetonitrile was removed in vacuo and the residue waspartitioned between saturated sodium bicarbonate solution (400 mL) anddichloromethane 44×400 mL). The organic layers were combined andconcentrated in vacuo. The resulting residue was dissolved in ethylacetate (200 mL) and started to precipitate a solid. Hexanes (300 mL)was added and additional solid precipitated. The solid was collected byfiltration and washed with hexanes (2×200 mL) and dried in vacuo to give63.5 g which was used as is without further purification.

[0169] ii. 5-methyl-1-(2-fluoro-β-D-erythro-pentofuranosyl)-cytosine

[0170]4-Triazine-1-(3′,5′-di-O-acetyl-2-fluoro-β-D-erythro-pentofuranosyl)-thymine(75.5 g,0.198 mol) was dissolved in ammonia (400 mL) in a stainlesssteel bomb and sealed overnight. The bomb was cooled and opened and theammonia was evaporated. Methanol was added to transfer the material to aflask and about 10 volumes of ethyl ether was added. The mixture wasstirred for 10 minutes and then filtered. The solid was washed withethyl ether and dried to give 51.7 g (86%) of the title compound.

[0171] iii.4-N-Benzoyl-5-methyl-1-(2-fluoro-β-D-erythro-pento-furanosyl)cytosine

[0172] 5-Methyl-1-(2-fluoro-β-D-erythro-pentofuranosyl)-cytosine (54.6g, 0.21 mol) was suspended in pyridine (700 mL) and benzoic anhydride(70 g, 0.309 mol) was added. The mixture was stirred for 48 hours atroom temperature. The pyridine was removed by evaporation and methanol(800 mL) was added and the mixture was stirred. A precipitate formedwhich was filtered, washed with methanol (4×50 mL), washed with ether(3×100 mL), and dried in a vacuum oven at 45° C. to give 40.5 g of thetitle compound. The filtrate was concentrated in vacuo and treated withsaturated methanolic ammonia in a bomb overnight at room temperature.The mixture was concentrated in vacuo and the resulting oil was purifiedby silica gel column chromatography. The recycled starting material wasagain treated as above to give an additional 4.9 g of the title-compoundto give a combined 45.4 g (61%) of the title compound.

[0173] iv.4-N-Benzoyl-5-methyl-1-(2-fluoro-5-O-dimethoxytrityl-β-D-erythro-pentofuranosyl)cytosine

[0174]4-N-Benzoyl-5-methyl-1-(2-fluoro-β-D-erythro-pentofuranosyl)-cytosine(45.3 g,0.124 mol) was dissolved in 250 ml dry pyridine anddimethoxytrityl chloride (46.4 g, 0.137 mol) was added. The reactionmixture was stirred at room temperature for 90 minutes and methanol (20mL) was added. The mixture was concentrated in vacuo and partitionedbetween ethyl acetate (2×1 L) and saturated sodium bicarbonate (1 L).The ethyl acetate layers were combined, dried over magnesium sulfate andevaporated in vacuo. The resulting oil was dissolved in dichloromethane(200 mL) and purified by silica gel column chromatography using ethylacetate/hexane/triethyl amine 50:50:1. The product fractions were pooledconcentrated in vacuo dried to give 63.6 g (76.6%) of the titlecompound.

[0175] v.4-N-Benzoyl-5-methyl-1-(2-fluoro-3-O-N,N-diisopropyl-amino-2-cyanoethylphosphite-5-O-dimethoxytrityl-β-D-erythro-pentofuranosyl)cytosine

[0176]4-N-Benzoyl-5-methyl-1-(2-fluoro-5-O-dimethoxy-trityl-β-D-erythro-pentofuranosyl)-cytosine(61.8 g, 92.8 mmol) was stirred with dichloromethane (300 mL),2-cyanoethyl N,N,N′,N′-tetraisopropylphosphorodiamidite (40.9 mL, 0.130mol) and diisopropylamine t

,0.3 eq.) at room temperature for 17 hours

washed with saturated sodium bicarbo

bicarbonate solution was back extract

ethane (500 mL). The combined organic layer

brine (1 L) and the brine was back

dichloromethane (100 mL). The combin

were dried over sodium sulfate, filtered,

to a vol of about 200 mL. Tht resulting

by silica gel column chromatography usi

acetate/triethyl amine 60/40/1. The

were concentrated in vacuo, dissolved in

filtered, concentrated in vacuo, and

foam was chopped and dried for 24 ho

weight to give 72.4 g (90%) of the title c

Cl₃) δ1.17-1.3 (m, 12 H, 4×CH₃), 1.5-1.6 (

-2.4 (t, 1 H, CH₂CN), 2.6-2.7 (t, 1 H, CH

, 2×CH₃OAr, 5′ CH₂, CH₂OP, C-5 CH₃), 4.

4.7 (m, 1 H, 3′), 5.0-5.2 (m, 1 H,

1′), 6.8-6.9 (m, 4 H, DMT), 7.2-7.6

), 7.82-7.86 (d, 1 H, C-6), 8.2-8.3 (d,

(CDCl₃); bs, 151.706; bs, 151.941.

EXAMPLE 5-c

[0177] i. 1-(2,3-di-O-Butyltin-β-D-erytbro

5-methyluridine

[0178] 5-Methyluridine (7.8 g, 30

tin oxide (7.7 g, 30.9 mmol) were suspe

mL) and heated to reflux for 16 hours.

was cooled to room temperature, filtered

washed with methanol (2×150 mL). The re

dried to give 12.2 g (80.3%) of the title

terial was used without further purificati

reactions. NMR was consistent with

[0179] ii. 1-(2-O-Propyl-β-D-exythro-pentofuranosyl)-5-methyl-uridine

[0180] 1-(2,3-di-O-butyltin-β-D-erythro-pentofuranosyl)-5-methyluridine(5.0 g, 10.2 mmol) and iodopropane (14.7 g, 72.3 mmol) were stirred inDMF at 100° C. for 2 days. The reaction mixture was cooled to roomtemperature and filtered and concentrated. The residual DMF wascoevaporated with acetonitrile. After drying the residue there wasobtained 2.40 g (78%) of the title compound and the 3′-O-propyl isomeras a crude mixture. This material was used without further purificationin subsequent reactions.

[0181] iii.1-(2-O-Propyl-5-O-Dimethoxytrityl-β-D-exythro-pento-furanosyl)-5-methyluridine

[0182] 1-(2-O-Propyl-β-D-erythro-pentofuranosyl)-5-methyluridine and the3′-O-propyl isomer as a crude mixture (2.4 g, 8.4 mmol) was coevaporatedwith pyridine (2×40 mL) and dissolved in pyridine (60 mL). The solutionwas stirred at room temperature under argon for 15 minutes anddimethoxytrityl chloride (4.27 g, 12.6 mmol) was added. The mixture waschecked periodically by tlc and at 3 hours was completed. Methanol (10mL) was added and the mixture was stirred for 10 minutes. The reactionmixture was concentrated in vacuo and the resulting residue purified bysilica gel column chromatography using 60:40 hexane/ethyl acetate with 1triethylamine used throughout. The pooling and concentration ofappropriate fractions gave 1.32 g (26%) of the title compound.

[0183] iv.1-(2-O-Propyl-3-O-N,N-Diisopropylamino-2-cyanoethyl-phosphite-5-O-Dimethoxytrityl-β-D-erythro-Pentofuranosyl)-5-methyluridine

[0184]1-(2-O-Propyl-5-O-dimethoxytrityl-β-D-erythro-pentofuranosyl)-5-methyluridine(50.0 g, 86 mmol),2-cyano-ethyl-N,N,N′,N′-tetra-isopropylphosphorodiamidite (38 mL, 120mmol), and diisopropylamine tetrazolide (4.45 g, 25.8 mmol) weredissolved in dichloromethane (500 mL) and stirred at room temperaturefor 40 hours. The reaction mixture was washed with saturated sodiumbicarbonate solution (2×400 mL) and brine (1×400 mL). The aqueous layerswere back extracted with dichloromethane. The dichloromethane layerswere combined, dried over sodium sulfate, filtered, and concentrated invacuo. The resultant residue was purified by silica gel columnchromatography using ethyl acetate/hexane 40:60 and 1% triethylamine.The appropriate fractions were pooled, concentrated, and dried underhigh vacuum to give 43 g (67%).

[0185] v.1-(2-O-Propyl-3-O-acetyl-5-O-dimethoxytrityl-β-D-erythro-pentofuranosyl)-5-methyluridine

[0186]1-(2-O-Propyl-5-dimethoxytrityl-β-D-erythro-pento-furanosyl)-5-methyluridine(10.0 g, 16.6 mmol) was dissolved in pyridine (50 mL) and aceticanhydride (4.7 ml, 52.7 mmol) was added. The reaction mixture wasstirred for 18 hours and excess acetic anhydride was neutralized withmethanol (10 mL). The mixture was concentrated in vacuo and theresulting residue dissolved in ethyl acetate (150 mL). The ethyl acetatewas washed with saturated NaHCO₃ (150 mL) and the saturated NaHCO₃ washwas back extracted with ethyl acetate (50 mL). The ethyl acetate layerswere combined and concentrated in vacuo to yield a white foam 11.3 g.The crude yield was greater than 100% and the NMR was consistent withthe expected structure of the title compound. This material was usedwithout further purification in subsequent reactions.

EXAMPLE 5-d

[0187] i.1-(2-O-Propyl-3-O-acetyl-5-O-dimethoxytrityl-β-D-erythro-pentofuranosyl)-4-triazolo-5-methylpyrimidine

[0188] Triazole (10.5 g, 152 mmol) was dissolved in acetonitrile (120ml) and triethylamine (23 mL) with stirring under anhydrous conditions.The resulting solution was cooled in a dry ice acetone bath andphosphorous oxychloride (3.9 mL, 41 mmol) was added slowly over a periodof 5 minutes. The mixture was stirred for an additional 10 minutesbecoming a thin slurry indicative of product formation.1-(2-O-Propyl-3-O-acetyl-5-O-dimethoxytrityl-β-D-erythro-pentofuranosyl)-5-methyluridine(11.2 g, 165mmol) was dissolved in acetonitrile (150 mL) and added tothe slurry above, maintaining dry ice acetone bath temperatures. Thereaction mixture was stirred for 30 minutes and then allowed to warm toroom temperature and stirred for an additional 2 hours. The mixture wasplaced in a freezer at 0° C. for 18 hours and then removed and allowedto warm to room temperature. Tlc in ethyl acetate/hexane 1:1 of themixture showed complete conversion of the starting material. Thereaction mixture was concentrated in vacuo and redissolved in ethylacetate (300 mL) and extracted with saturated sodium bicarbonatesolution (2×400 mL) and brine (400 mL). The aqueous layers were backextracted with ethyl acetate (200 mL). The ethyl acetate layers werecombined, dried over sodium sulfate, and concentrated in vacuo. Thecrude yield was 11.3 g (95%). The NMR was consistent with the expectedstructure of the title compound. This material was used without furtherpurification in subsequent reactions.

[0189] ii.1-(2-O-Propyl-5-O-dimethoxytrityl-β-D-exythro-pento-furanosyl)-5-methylcytidine

[0190]1-(2-O-Propyl-3-O-acetyl-5-O-dimethoxytrityl-β-D-erythro-pentofuranosyl)-4-triazolo-5-methylpyrimidine(11.2 g, 16.1 mmol) -was dissolved in liquid ammonia (50 mL) in a 100 mLbomb at dry ice acetone temperatures. The bomb was allowed to warm toroom temperature for 18 hours and then recooled to dry ice acetonetemperatures. The bomb contents were transferred to a beaker andmethanol (50 mL) was added. The mixture was allowed to evaporate to neardryness. Ethyl acetate (300 mL) was added and some solid was filteredoff prior to washing with saturated sodium bi-carbonate solution (2×250mL). The ethyl acetate layers were dried over sodium sulfate, filtered,combined with the solid previously filtered off, and concentrated invacuo to give 10.1 g of material. The crude yield was greater than 100%and the NMR was consistent with the expected structure of the titlecompound. This material was used without further purification insubsequent reactions.

[0191] iii.1-(2-O-Propyl-5-O-dimethoxytrityl-O-D-exythro-pento-furanosyl)-4-N-benzoyl-5-methylcytidine

[0192]1-(2-O-Propyl-5-O-dimethoxytrityl-β-D-erythro-pentofuranosyl)-5-methylcytidine(7.28 g, 10.1 mmol) and benzoic anhydride (4.5 g, 20 mmol) weredissolved in DMF (60 mL) and stirred at room temperature for 18 hours.The reaction mixture was concentrated in vacuo and redissolved in ethylacetate (300 mL). The ethyl acetate solution was washed with saturatedsodium bicarbonate solution (2×400 mL), dried over sodium sulfate,filtered, and concentrated in vacuo. The residue was purified by silicagel column chromatography using ethyl acetate/hexane 1:2 and 1%triethylamine. The appropriate fractions were pooled, concentrated, anddried under high vacuum to give 5.1 g (59% for 4 steps starting with the1-(2-O-propyl-dimethoxytrityl-β-D-erythro-pentofuranosyl)-5-methyluridine).

[0193] iv.1-(2-O-Propyl-3-O-N,N-diisopropylamino-2-cyanoethyl-phosphite-5-O-dimethoxytrityl-β-D-exythro-pentofuranosyl)-4-N-benzoyl-5-methylcytidine

[0194]1-(2-O-Propyl-5-O-dimethoxytrityl-β-D-erythro-pentofuranosyl)-4-N-benzoyl-5-methylcytidine(5.0 g, 7 mmol),2-cyanoethyl-N,N,N′,N′-tetra-isopropylphosphorodiamidite (3.6 mL, 11.3mmol), and diisopropylaminotetrazolide (0.42 g, 2.4 mmol) were dissolvedin dichloromethane (80 mL) and stirred at room temperature for 40 hours.The reaction mixture was washed with saturated sodium bicarbonatesolution (2×40 mL) and brine (1×40 mL). The aqueous layers were backextracted with dichloromethane. The dichloromethane layers werecombined, dried over sodium sulfate, filtered, and concentrated invacuo. The resultant residue was purified by silica gel columnchromatography using ethyl acetate/hexane 40:60 and 1% triethylamine.The appropriate fractions were pooled, concentrated, and dried underhigh vacuum to give 7.3 g (98%).

EXAMPLE 5-e

[0195] i. 2′-O-Methyl-5-methyluridine

[0196] Procedure 1:

[0197] Crude 2,2′-anhydro-5-methyluridine (10.0 g, 0.0416 mol) (Example2-a) was dissolved in methanol (80 mL) in a stainless steel bomb (100 mLcapacity). Trimethyl borate (5.6 mL, 0.049 mol) was added (Note 1). Thebomb was sealed and placed in an oil bath at 150° C. which generated apressure of about 5 atm. After 40 h, the bomb was cooled in ice, openedand the contents concentrated under reduced pressure to a tan foam, 12g. NMR of the crude was consistent with the product contaminated withimpurities in the starting material and a trace of thymine and startingmaterial (Note 2). The crude product was used as is for the next step.

[0198] The trialkyl borates can be conveniently generated by addingsolutions (eg 1 M in THF) of borane to the desired alcohol and allowingthe resulting hydrogen gas to evolve.) The nucleoside can be purified atthis point by column chromatography using a gradient of methanol inethyl acetate (0-10%) and crystallizing the product from absoluteethanol to give white needles, mp 192-193° (mp 197-198°). Literaturereference for the melting point of this compound is contained in E.Ootsuka, H. Inoue, Japanese Patent 89-85456, Apr. 4, 1989.

[0199] Procedure 2:

[0200] Pure 2,2′-anhydro-5-methyluridine (1.0 g, 4.16 mmol) andtrimethylborate (0.56 mL, 4.9 mmol) was dissolved in methanol (20 mL) ina stainless steel bomb (100 mL). The bomb was placed in an oil bath at150° C. After 80 h, TLC indicating the reaction to be mostly complete.The solvent was removed yielding a white foam. NMR indicated product tostarting material ratio of 93:7 with no other impurities noted. Theresidue was purified by silica gel column chromatography using amethanol gradient in ethyl acetate (0-10%) yielding 850 mg (75%) of pureproduct and 250 mg of still contaminated product. An analytically puresample was prepared for NMR. ¹H NMR (DMSO-d₆): δ1.79 (s, 3H, 5-CH₃),3.35 (s, 3H, OCH₃), 3.5-3.7 (m, 2H, H-5′), 3.7-3.9 (m, 2H, H-3′,4′),4.15 (m, 1H, H-2′), 5.17 (m, 2H, 3′,5′-OH), 5.87 (d, J=5 Hz, 1H, H-1′),7.80 (s, 1H, H-6), 11.37 (br s, 1H, N—H) . Anal. Calcd for C₁₁H₁₆N₂O₆(272.26): C, 48.52; H, 5.92; N, 10.29. Found: C, 48.56; H, 5.88; N,10.22.

[0201] Procedure 3:

[0202] The same as described for procedure 2 except 30 mg of sodiumbicarbonate was added to the reaction (to match the sodium content ofthe crude anhydro) which allowed the reaction to be complete in 24 h.Ammonium chloride (50 mg) was added to neutralize the base and thesolution was stripped to dryness. NMR of the crude indicated threeminor( nucleoside impurities (total about 6%). After a similar columnand then crystallizing the residue from methanol/ethyl acetate, thereremained 850 mg of first crop material and 120 mg of second cropmaterial both with 2-3% of unknown nucleoside impurities for a stillcontaminated yield of 85%.

[0203] ii. 5′-O-Dimethoxytriphenylmethyl-2′-O-methyl-5-methyl-uridine

[0204] Crude 2′-O-methyl-5-methyl uridine (12 g) was coevaporated inpyridine (2×50 mL) and dissolved in dry pyridine (50 mL).Dimethoxytriphenylmethyl chloride (18.1 g, 0.054 mol) was added. theflask was stoppered and allowed to stand for 45 min at room temperature.Methanol (10 mL) was added to quench the reaction and the solution wasconcentrated under reduced pressure to an oil. The residue waspartitioned between ethyl acetate (2×400 mL) and saturated sodiumbicarbonate solution (500 mL). The organic layers were combined, dried(sodium sulfate), filtered and concentrated to a yellow foam. The foamwas dissolved in methylene chloride (60 mL) and put onto a silica gelcolumn (300 g) and eluted with ethyl acetate-hexanes-triethylamine,60:40:1. The product containing fractions were combined, concentratedand coevaporated with dry acetonitrile (2×50 mL). The resulting residuewas dried at 1 mm Hg for 24 h to a crisp white foam, 17.0 g (60.4% inthree steps from 5-methyluridine).

EXAMPLE 5-f

[0205] i. 2,3,5-Tri-O-benzoyl-2-thio-5-methyluridine

[0206] In a 250 ml 3 neck round bottomed flask1-O-acetyl-2,3,5-tri-O-benzoyl ribose (0.500 g, 1 mmol) and5-methyl-2-thiouracil (0.156 g, 1.1 mmol) was dried under vacuumovernight. These components were dissolved in 10 mL of dry acetonitrileand heated to 80° C. To this warm solution was addedN-O-bis(trimethylsilyl)acetamide (0.509 g, 2.5 mmol) and the reactionstirred for 1 hr at 80° C. The reaction mixture was removed from theheat and allowed to cool to room temperature, and trimethyl silyltriflate (0.334 g, 1.5 mmol) was added dropwise. The reaction mixturewas then heated to 50° C. and stirred for 4 hours. The reaction mixturewas checked by TLC using ethyl acetate/hexane 1:1, which showed thereaction had gone to completion. The solution was cooled to roomtemperature and partitioned between 50 mL of dichloromethane and 50 mLof saturated sodium bicarbonate solution. The aqueous phase wasextracted two more times with dichloromethane and the organic layerscombined, dried with magnesium sulfate and concentrated to a pale yellowfoam. This foam was used without further purification.

[0207] ii. 2-Thio-5-methyluridine

[0208] The crude 2,3,5-tri-O-benzoyl-2-thio-5-methyl uridine (20 g, 37mmoles) was dissolved in 500 mL of methanol. To this solution was addedsodium methoxide (2.0 g, 37 mmoles) and the reaction stirred for 2hours. The reaction was checked by TLC using ethyl acetate/hexane 1:1and ethyl acetate/methanol 9:1, which showed the reaction had gone tocompletion. Dowex 50 H⁺ resin was added until the solution was neutralby pH paper and the resin filtered. The resin was then washed with 100ml of additional methanol and the combined filtrates were concentratedto give the title compound 8.5 g, (84%) as a pale yellow foam.

EXAMPLE 5-g

[0209] 2′-O-Methyl-5-methyl-2-thiouridine

[0210] To a stirred solution of 5-methyl-2-thiouridine (0.500 g, 1.8mmol) in DMF (10 ml) is added dibutyltin oxide (0.500 g, 2.0 mmol),tetrabutyl ammonium iodide (0.738 g, 2 mmol), and methyl iodide (1.022g, 7.2 mmol). The reaction flask is sealed and heated at 50° C. for 16hours. The mixture is cooled and another portion of methyl iodide isadded (1.022 g, 7.2 mmol) and the reaction heated for an additional 16hours. At the end of this time, the reaction mixture is cooled to roomtemperature and diluted with methylene chloride and chromatographedusing a methylene chloride/methanol gradient. The appropriate fractionsare collected and concentrated to give2′-O-methyl-5-methyl-2-thiouridine.

EXAMPLE 5-h

[0211] 2′-O-Propyl-5-methyl-2-thiouridine

[0212] The title compound is prepared as per the procedures of Example5-g by substituting propyl iodide (1.22 g, 7.2 mmoles) in place ofmethyl iodide.

Example 5-i

[0213] i. 2′-O-phthalimidopropyl-5-methyl-2-thiouridine

[0214] The title compound was prepared as per the procedures of Example5-g by substituting bromo-propyl phthalimide (0.67 g, 2.5 mmoles) inplace of methyl iodide, with an additional (0.300 g) added on the secondday.

[0215] ii. 5′-O-Dimethoxytrityl-2′-O-propylamine-5-methyl-2-thio-uridine

[0216] 2′-O-Phthalimidopropyl-5-methyl-2-thiouridine (2.6 g, 3.6 mmol)was dissolved in dry pyridine and co-evaporated twice. The resultingfoam was dissolved in 25 mL of dry pyridine and dimethoxy-tritylchloride (1.8 g, 5.5 mmol) was added followed by4,4-dimethylaminopyridine (0.050 g, 0.4 mmol). The reaction was allowedto stir overnight at room temperature: To the reaction mixture was added1 mL of methanol. The solution was partitioned between 75 mL ofsaturated sodium bicarbonate and 50 mL of chloroform. The aqueous layerwas extracted with two additional portions of chloroform and the organiclayers combined and dried with magnesium sulfate. After removal of thedrying agent via filtration the filtrate was concentrated to an orangeoil and purified by silica gel column chromatography usingmethanol/chloroform gradient with 0.5% pyridine added to neutralize thesilica gel.

[0217] iii.5′-O-Dimethoxytrityl-2′-O-propylamine-5-methyl-2S-toluoyl-2-thiouridine

[0218] 5′-O-Dimethoxytrityl-2′-O-propylamine-5-methyl-2-thiouridine (1g, 1.6 mmol) was dissolved in DMF and cooled to 0° C. To this solutionwas added triethyl amine (0.300 g, 3 m.mol) followed by toluoyl chloride(0.300 g, 1.92 mmol) dropwise over 5 minutes. The reaction was thenallowed to warm to room temperature and stirred overnight, when completethe reaction was quenched with methanol and concentrated to an oil. Theoil was then partitioned between 250 mL of a solution of saturatedsodium bicarbonate/chloroform 1:1. The aqueous layer was extracted withtwo additional, 75 mL portions of chloroform, and the organic layerswere dried and concentrated to an oil. The protected nucleoside waspurified by silica gel column chromatography using a hexane/ethylacetate gradient. The desired product was collected as a mixture of N-3toluoyl and S-2 Toluoyl compounds. This mixture was used as is for thephosphyt-ilation procedure.

[0219] iv.5′-O-Dimethoxytrityl-2′-O-propylamine-3′-O-[(N,N-diisopropylamino)-2-cyanoethoxyphosphite]-5-methyl-2-S-toluoyl-2-thiouridine

[0220] To a solution of5′-O-dimethoxytrityl-2′-O-propyl-amine-5-methyl-2-S-toluoyl-2-thiouridine(16.01 g, 22 mmol) and diisopropylethylamine (10 ml) in THF (200 ml), at0° C., is added chloro-β-cyanoethoxy-N,N-diisopropylaminophosphine (5.6ml, 25 mmol). The reaction mixture was stirred at room temperature for20 hours. The reaction was concentrated and the residue purified bysilica gel column chromatography. Elution with an ethyl acetate/hexanegradient while maintaining 1% triethylamine, pooling of appropriatefractions and evaporation will give the title compound.

EXAMPLE 5-j

[0221] i. 2′-O-Aminopropyl-5-methyl-2-thiouridine

[0222] 2′-O-Phthalimidopropyl-5-methyl-2-thiouridine (5.0 g, 15.8 mmol)is dissolved in 100 ml methanol in a 500 ml flask. Hydrazine (2.02 g,63.2 mmol) is added and the mixture is heated to reflux (60-65° C.) withstirring for 14 hours. The solvent is evaporated in vacuo and theresidue is dissolved in dichloromethane (150 ml) and extracted twicewith an equal volume NH₄OH. The organic layer is evaporated to yield thecrude product. NMR is used to assay product purity. The product is usedin subsequent reactions without further purification.

[0223] ii. 2′-O-Trifluoroacetylaminopropyl-5-methyl-2-thiouridine

[0224] 2′-O-Aminopropyl-5-methyl-2-thiouridine is dissolved in MeOH and5 equivalents of triethylamine are added followed by 10 equivalents ofethyl trifluoroacetate. The title compound is isolated afterpurification.

[0225] iii.2′-O-Trifluoroacetylaminopropyl-5′-O-dimethoxytrityl-5-methyl-2-thiouridine

[0226] 2′-O-Trifluoroacetylaminopropyl-5-methyl-2-thio-uridine (2.5 g,3.6 mmol) is dissolved in dry pyridine and co-evaporated twice. Theresulting yellow foam is dissolved in 25 mL of dry pyridine anddimethoxytrityl chloride (1.8 g, 5.5 mmol) is added followed by4,4-dimethylaminopyridine (0.050 g, 0.4 mmol). The reaction is allowedto stir overnight at room temperature. To the reaction mixture is added1 mL of methanol. The solution is partitioned between 75 mL of saturatedsodium bicarbonate and 50 mL of chloroform. The aqueous layer isextracted with two additional portions of chloroform and the organiclayers combined and dried with magnesium sulfate. After removal of thedrying agent via filtration the filtrate is concentrated to an oil andpurified by silica gel column chromatography using methanol/chloroformgradient with 0.5% pyridine added to neutralize the silica gel to givethe title compound.

[0227] iv.0.2′-O-Trifluoroacetylaminopropyl-3′-O-[(N,N-diisopropyl-amino)-2-cyanoethoxyphosphite]-5′-O-dimethoxytrityl-5-methyl-2-thiouridine

[0228] The title compound is prepared as per the procedure of Example5-i-iv. using the title compound from Example 5-j-iii.

EXAMPLE 5-k

[0229] i. 5′-O-Dimethoxytrityl-2-thio-5-methyluridine

[0230] 2-Thio-5-methyl uridine (1 g, 3.6 mmol) was dissolved in drypyridine and co-evaporated twice. The resulting yellow foam wasdissolved in 25 mL of dry pyridine and dimethoxy-trityl chloride (1.8 g,5.5 mmol) was added followed by 4,4-dimethylaminopyridine (0.050 g, 0.4mmol). The reaction was allowed to stir overnight at room temperature.To the reaction mixture was added 1 mL of methanol. The solution waspartitioned between 75 mL of saturated sodium bicarbonate and 50 mL ofchloroform. The aqueous layer was extracted with two additional portionsof chloroform and the organic layers combined and dried with magnesiumsulfate. After removal of the drying agent via filtration the filtratewas concentrated to an orange oil and purified by silica gel columnchromatography using methanol/chloroform gradient with 0.5% pyridineadded to neutralize the silica gel.

[0231] ii.5′-O-Dimethoxytrityl-3′-t-butyldimethylsilyl-5-methyl-2-thiouridine

[0232] 5′-O-Dimethoxytrityl-2-thio-5-methyl uridine (1 g, 1.73 mmol) wasco-evaporated twice with dry DMF and then dissolved in dry DMF andimidazole (0.141 g, 2.08 mmol) was added followed by (0.313 g, 2.08mmol) of t-butyl-dimethylsilyl chloride. The reaction mixture wasstirred overnight. The reaction was checked by TLC using ethylacetate/hexane 1:1, which showed the reaction had gone to completion.The reaction mixture was then poured into 5% sodium bicarbonate andextracted 3 times with chloroform. The combined organic solution wasdried with magnesium sulfate and concentrated to an oil. The resultingoil was purified by silica gel column chromatography using amethanol/chloroform gradient isolating separately the 2′ and 3′ silylprotected nucleoside.

[0233] iii.5′-O-Dimethoxytrityl-3′-t-butyldimethylsilyl-2′-methanesulfonyl-5-methyl-2-thiouridine

[0234]5′-O-Dimethoxytrityl-3′-t-butyldimethylsilyl-5-methyl-2-thiouridine (1.0g, 1.45 mmoles) was dissolved in pyridine and cooled to 0° C. To thissolution was added methanesulfonyl chloride (0.183 g, 1.6 mmoles)dropwise. The reaction was then allowed to stir until complete by TLC.The reaction mixture is neutralized with methanol and concentrated to anoil. The title compound is used as is for further reactions.

[0235] iv. 5′-Dimethoxytrityl-3′-t-butyldimethylsilyl-2,2′-thioanhydro-5-methyl-2-thiouridine

[0236] The mesylated nucleoside found in Example 5-k-iii is treated atroom temperature with 5 equivalents of sodium methoxide and allowed tostir until complete formation of the thioanhydro product. The solutionis then neutralized with Dowex 50W (H⁺ form), the resin filtered off andthe resulting solution concentrated to give the title compound.

[0237] v.2′-Fluoro-3′-t-butyldimethylsilyl-5′-Dimethoxytrityl-5-methyl-2-thiouridine

[0238] The thioanhydronucleoside found in Example 5-k-iv was dissolvedin anhydrous dioxane. To this solution was added 6 equivalents ofHF/Pyridine complex and the reaction stirred until complete by TLC. Thereaction mixture is then poured over an equal volume of ice and calciumcarbonate is added until neutral. The solids are filtered off and thefiltrate is concentrated. The residue is purified by silica gel columnchromatography to give the title compound.

[0239] vi.2′-Fluoro-3′-O-[(N,N-diisopropylamino)-2-cyanoethoxy-phosphite]-5′-dimethoxytrityl-5-methyl-2-thiouridine

[0240]2′-Fluoro-3′-t-butyldimethylsilyl-5′-dimethoxy-trityl-5-methyl-2-thiouridineis treated as per the procedure of Example 5-i-iv. to give the titlecompound.

EXAMPLE 6

[0241] Oligoribonucleotide Synthesis

[0242] Unsubstituted and substituted phosphodiesteroligoribonucleotides, also identified herein as PO linkedoligoribonucleotides, were synthesized on an automated DNA synthesizer(Applied Biosystems model 380B) using standard phosphoramidite chemistrywith oxidation by iodine.

[0243] Phosphorothioate oligonucleotides, also identified herein as PSlinked oligoribonucleotides, are synthesized as per the phosphodiesteroligoribonucleotides except the standard oxidation bottle was replacedby 0.2 M solution of 3H-1,2-benzodithiole-3-one 1,1-dioxide inacetonitrile for the step wise thiation of the phosphite linkages. Thethiation wait step was increased to 68 sec and was followed by thecapping step. After cleavage from the CPG column and deblocking inconcentrated ammonium hydroxide at 55° C. (18 hr), the oligonucleotideswere purified by precipitating twice with 2.5 volumes of ethanol from a0.5 M NaCl solution. Analytical gel electrophoresis was accomplished in20% acrylamide, 8 M urea, 454 mM Tris-borate buffer, pH=7.0.Oligonucleotides and phosphorothioates were judged, based onpolyacrylamide gel electrophoresis, to be greater than 80% full-lengthmaterial.

[0244] Phosphinate oligoribonucleotides, also identified herein as PIlinked oligoribonucleotides, are prepared as is described in U.S. Pat.No. 5,508,270, herein incorporated by reference.

[0245] Alkyl phosphonate oligoribonucleotides, also identified herein asPMe linked oligoribonucleotides, are prepared as is described in U.S.Pat. No. 4,469,863, herein incorporated by reference.

[0246] Phosphoramidite oligoribonucleotides, also identified herein asPN linked oligoribonucleotides, are prepared as is described in U.S.Pat. No., 5,256,775 or U.S. Pat. No. 5,366,878, herein incorporated byreference.

[0247] Alkylphosphonothioate oligoribonucleotides, also identifiedherein as MePS linked oligoribonucleotides, are prepared as is describedin published PCT applications PCT/US94/00902 and PCT/US93/06976(published as WO 94/17093 and WO 94/02499, respectively), hereinincorporate by reference.

[0248] 3′-Deoxy-3′-amino phosphoramidate oligoribonucleotide, alsoidentified herein as 3′NPN linked oligoribonucleotides, are prepared asis described in U.S. Pat. No. 5,476,925, herein incorporated byreference.

[0249] Phosphotriester oligoribonucleotides, also identified herein asPOMe linked oligoribonucleotides, are prepared as is described in U.S.Pat. No. 5,023,243, herein incorporated by reference.

[0250] Borano phosphate oligoribonucleotide, also identified herein asBP linked oligoribonucleotides, are prepared as is described in U.S.Pat. Nos. 5,130,302 and 5,177,198, both herein incorporated byreference.

EXAMPLE 7-a

[0251] Oligoribonucleoside Synthesis

[0252] Methylenemethylimino linked oligoribonucleosides, also identifiedherein as MMI linked oligoribonucleosides, methylenedimethylhydrazolinked oligoribonucleosides, also identified herein as MDH linkedoligoribonucleosides, and methylenecarbonylamino linkedoligonucleosides, also identified herein as amide-3 linkedoligoribonucleosides, and methyleneaminocarbonyl linkedoligonucleosides, also identified herein as amide-4 linkedoligoribonucleosides as well as mixed backbone compounds having, as forinstance, alternating MMI and PO or PS linkages are prepared as isdescribed in U.S. Pat. Nos. 5,378,825, 5,386,023, 5,489,677 and inpublished PCT applications PCT/US92/04294 and PCT/US92/04305 (publishedas WO 92/20822 WO and 92/20823, respectively), herein incorporated byreference.

[0253] Formacetal and thioformacetal linked oligoribonucleosides, alsoidentified herein as FA and TFA oligoribonucleosides, respectively, areprepared as is described in U.S. Pat. Nos. 5,264,562 and 5,264,564,herein incorporated by reference.

[0254] Ethylene oxide linked oligoribonucleosides, also hereinidentified as ETO linked oligoribonucleosides, are prepared as isdescribed in U.S. Pat. No. 5,223,618, herein incorporated by reference.

EXAMPLE 7-b

[0255] PNA

[0256] Peptide Nucleic Acids (PNAs) are known per se and are prepared inaccordance with any of the various procedures referred to in PeptideNucleic Acids (PNA): Synthesis, Properties and Potential Applications,Bioorganic & Medicinal Chemistry, 1996, 4, 5-23. They may also beprepared in accordance with U.S. Pat. No. 5,539,083, corresponding toSer. No. 08/200,742, filed Feb. 23, 1994, and assigned to the sameassignee as this application. These references are herein incorporatedby reference.

EXAMPLE 8

[0257] Chimeric phosphorothioate oligoribonucleotides, e.g.[2′-O-Me]/PS.[2′-OH]/PS.[−2′-O-Me]/PS oligoribonucleotide

[0258] Chimeric oligoribonucleotides having 2′-O-alkyl phosphorothioateand 2′-OH phosphorothioate oligonucleotides segments were synthesizedusing an Applied Biosystems automated DNA synthesizer Model 380B, asabove. Oligoribonucleotides were synthesized using the automatedsynthesizer and 5′-dimethoxytrityl-2′-tert-butyldimethylsilyl3′-O-phosphoramidite for the RNA portion and5′-dimethoxytrityl-2′-O-methyl-3′-0-phosphroamidite for 5′ and 3′ wings.The protecting groups on the exocyclic amines were, phenoxyacetyl for rAand rG, benzoyl for rC and 2′-O-methyl A and 2′-O-methyl C, andisobutyryl for 2′-O-methyl G. The standard synthesis cycle was modifiedby increasing the wait step after the delivery of tetrazole and base to600 s repeated four times for RNA and twice for 2′-0-methyl. The fullyprotected oligoribonucleotide was cleaved from the support and thephosphate group was deprotected in 3:1 Ammonia/Ethanol at roomtemperature overnight then lyophilized to dryness. Treatment inmethanolic ammonia for 24 hrs at room temperature was then done todeprotect all bases and sample was again lyophilized to dryness. Thepellet was resuspended in 1M TBAF in THF for 24 hrs at room temperatureto deprotect the 2′ positions. The reaction is then quenched with 1MTEAA and the sample is then reduced to ½ volume by rotovac before beingdesalted on a G25 size exclusion column. The oligo recovered was thenanalyzed spectrophotometrically for yield and for purity by capillaryelectrophoresis and by mass spectrometer.

EXAMPLE 9

[0259] Chimeric “gapmer” oligoribonucleotides

[0260] i. Chimeric methyl phosphonate oligoribonucleotide e.g.,[2′-O-Me]/PMe.[2′-OH] /PMe.[−2′-O-Me]/PMe oligoribonucleotide

[0261] In the manner of Example 8, using oligoribonucleotides of Example6, a chimeric oligoribonucleotide having a methyl phosphonate backboneis prepared.

[0262] ii. Chimeric phosphoramidate oligoribonucleotide, e.g.,[2′-O-Me]/PN.[2′-OH]/PN.[−2′-O-Me]/PN oligoribonucleotide

[0263] In the manner of Example 8, using oligoribonucleotides of Example6, a chimeric oligoribonucleotide having a phosphoramidate backbone isprepared.

[0264] iii. Chimeric phosphoramidate oligoribonucleotide, e.g.,[2′-O-Me]/3′NPN.[2′-OH]/3′NPN.[-2′-O-Me]/3′NPN oligoribonucleotide

[0265] In the manner of Example 8, using oligoribonucleotides of Example6, a chimeric oligoribonucleotide having a 3′-deoxy-3′-aminophosphoramidate backbone is prepared.

[0266] iv. Chimeric phosphinate oligoribonucleotide, e.g.,[2′-O-Me]/PI.[2′-OH]/PI.[−2′-O-Me]/PI oligoribonucleotide

[0267] In the manner of Example 8, using oligoribonucleotides of Example6, a chimeric oligoribonucleotide having a phosphinate backbone isprepared.

[0268] v. Chimeric alkylphosphonothioate oligoribonucleotide, e.g.,[2′-O-Me]/MePS.[2′-OH]/MePS.[-2′-O-Me]/MePS oligoribonucleotide

[0269] In the manner of Example 8, using oligoribonucleotides of Example6, a chimeric oligoribonucleotide having a phosphonothioate backbone isprepared.

[0270] vi. Chimeric phosphorodithioate oligoribonucleotide, e.g.,[2′-O-Me]/P2S.[2′-OH]/P2S.[−2′-O-Me]/P2S oligoribonucleotide

[0271] In the manner of Example 8, using oligoribonucleotides of Example6, a chimeric oligoribonucleotide having a phosphorodithioate backboneis prepared.

[0272] vii. Chimeric phosphoselenate oligoribonucleotide, e.g.,[2′-O-Me]/PSe.[2′-OH]/PSe.[−2′-O-Me]/PSe oligoribonucleotide

[0273] In the manner of Example 8, using oligoribonucleotides of Example6, a chimerid oligoribonucleotide having a phosphoselenate backbone isprepared.

[0274] viii. Chimeric borano phosphate oligoribonucleotide, e.g.,[2′-O-Me]/BP.[2′-OH]/BP.[−2′-O-Me)/BP oligoribonucleotide

[0275] In the manner of Example 8, using oligoribonucleotides of Example6, a chimeric oligoribonucleotide having a borano phosphate backbone isprepared.

[0276] ix. Chimeric methyl phosphotriester oligoribonucleotide, e.g.,[2′-O-Me]/POME.[2′-OH]/POMe.[−2′-O-Me]/POMe oligoribonucleotide

[0277] In the manner of Example 8, using oligoribonucleotides of Example6, a chimeric oligoribonucleotide having a methyl phosphotriesterbackbone is prepared.

EXAMPLE 10

[0278] Chimeric Oligoribonucleosides

[0279] i. Chimeric methylenemethyimino oligoribonucleoside, e.g.[2′-O-Me]/MMI.[2′-OH]/MMI.[−2′-O-Me]/MMI oligoribonucleoside

[0280] In the manner of Example 8 using the chemistry of Example 7, achimeric oligoribonucleoside having methylenemethylimino linkagesthroughout the oligoribonucleoside is prepared.

[0281] ii. Chimeric methylenedimethyhydrazo oligoribonucleoside, e.g.[2′-O-Me]/MDH.[2′-OH]/MDH.[-2′-O-Me]/MDH oligoribonucleoside

[0282] In the manner of Example 8 using the chemistry of Example 7, achimeric oligoribonucleoside having methylenedimethylhydrazo linkagesthroughout the oligoribonucleoside is prepared.

[0283] iii. Chimeric formacetal oligoribonucleoside, e.g.[2′-O-Me]/FA.[2′-OH]/FA.[−2′-O-Me]/FA oligoribonucleoside

[0284] In the manner of Example 8 using the chemistry of Example 7, achimeric oligoribonucleoside having formacetal linkages throughout theoligoribonucleoside is prepared.

[0285] iv. Chimeric thioformacetal oligoribonucleoside, e.g.[2′-O-Me]/TFA.[2′-OH]/TFA.[−2′-O-Me]/TFA oligoribonucleoside In themanner of Example 8 using the chemistry of Example 7, a chimericoligoribonucleoside having thioformacetal linkages throughout theoligoribonucleoside is prepared.

[0286] v. Chimeric ethyleneoxide oligoribonucleoside, e.g.[2′-O-Me]/ETO.[2′-OH]/ETO.[−2′-O-Me]/ETO oligoribonucleoside

[0287] In the manner of Example 8 using the chemistry of Example 7, achimeric oligoribonucleoside having ethylene oxide linkages throughoutthe oligoribonucleoside is prepared.

[0288] vi. Chimeric methylenecarbonylamino oligoribonucleoside, e.g.[2′-O-Me]/amide-3.[2′-OH]/amide-3.[−2′-O-Me]/amide-3 oligoribonucleoside

[0289] In the manner of Example 8 using the chemistry of Example 7, achimeric oligoribonucleoside having amide-3 linkages throughout theoligoribonucleoside is prepared.

EXAMPLE 11

[0290] Chimeric oligoribonucleotides/oligoribonucleosides

[0291] i. Methylenemethylimino/phosphorothioate chimera, e.g.[2′-O-Me]/PS.[2′-OH]/PS.[−2′-O-Me]/MMIoligoribonucleoide/oligoribonucleoside

[0292] In the manner of Example 8 using the chemistry of Examples 6 and7, a chimeric compound having both oligoribonucleotide andoligoribonucleoside segments is prepared. The chimeric compounds hasmethylenemethylimino linkages in one “wing” and phosphorothioatelinkages in a central “gap” and in the other “wing.”

[0293] ii. Chimeric Methylphosphonate/methylenemethylimino/phos-phorothioateoligoribonucleotide/oligoribonucleoside, e.g.[2′-O-Me]/PMe.[2′-OH]/PS.[−2′-O-Me]/MMIoligoribonucleotide/oligoribonucleoside

[0294] In the manner of Example 8 using the chemistry of Examples 6 and7, a chimeric compound having both oligoribonucleotide andoligoribonucleoside portions is prepared. The chimeric compound hasmethylenemethylimino linkages in one “wing”, a phosphorothioate linkagesin a central “gap” and methyl phosphonate linkages in the other “wing.”

[0295] iii. Chimericmethylenecarbonylamino/phosphorothioate/methylenecarbonylaminooligoribonucleotide/oligoribo- nucleoside, e.g.[2′-O-Me]/amide-3.[2′-OH]/PS.[−2′-O-Me]/amide-3oligoribonucleotide/oligoribonucleoside

[0296] In the manner of Example 8 using the chemistry of Examples 6 and7, a chimeric compound having both oligoribonucleotide andoligoribonucleoside segments is prepared. The chimeric compound hasmethylenecarbonylaimino linkages in both “wings” and phosphorothioatelinkages in a central “gap.”

[0297] iv. Chimericmethylenecarbonylamino/phosphorothioate/methylenemethyliminooligoribonucleotide/oligoribonucleoside, e.g.[2′-O-Me]/amide-3.[2′-OH]/PS.[−2′-O-Me]/MMIoligoribonucleoide/oligoribonucleoside

[0298] In the manner of Example 8 using the chemistry of Examples 6 and7, a chimeric compound having both oligoribonucleotide andoligoribonucleoside segments is prepared. The chimeric compound hasmethylenecarbonylaimino linkages in one “wing” segment, phosphorothioatelinkages in a central “gap” segment and methylenecarbonylamino linkagesin the other “wing” segment.

[0299] v. Methylenemethylimino/phosphodiester/phosphorothioate chimera,e.g. [2′-O-Me]/MMI-PO.[2′-OH]/PS.[−2′-O-Me]/MMI-POoligoribonucleotide/oligoribonucleoside

[0300] In the manner of Example 8 using the chemistry of Examples 6 and7, a chimeric compound having both oligoribonucleotide andoligoribonucleoside segments is prepared. The chimeric compounds hasalternating methylenemethylimino and phosphodiester linkages in its“wing” segments and phosphorothioate linkages in its central “gap?segment.

EXAMPLE 12

[0301] Chimeric “end” gapped phosphorothioate oligoribonucleotides i.“3′-Endo gapped phosphorothioate chimera, e.g. [2′-O-Me]/PS.[2′-OH]/PSoligoribonucleotide

[0302] In the manner of Example 8 a chimeric compound having an “opengap” segment at its 3′ terminus,” a “wing” segment at its 5′ terminusand phosphorothioate linkages through out is prepared.

[0303] ii. “5′-End” gapped phosphorothioate chimera, e.g.[2′-OH]/PS.[2′-O-Me]/PS oligoribonucleotide

[0304] In the manner of Example 8 a chimeric compound having an “opengap” segment at its 5′ terminus,” a “wing” segment at its 3′ terminusand phosphorothioate linkages through out is prepared.

[0305] iii. “3′-End” gapped phosphorothioate chimera, e.g.[2′-F]/PS.[2′-OH]/PS oligoribonucleotide

[0306] In the manner of Example 8, a chimeric compound having an “opengap” at its 3′ terminus”, 2′-fluoro nucleosides in its 5′ “wing”segment, 2′-OH nucleosides in its open “gap” segment andphosphorothioate linkages through out is prepared.

EXAMPLE 13

[0307] Chimeric oligoribonucleotides with Uniform Backbone Linkages andVariable Nucleoside Subunits

[0308] i. Chimeric 2′-O-ethyl oligoribonucleotide, e.g.,[2′-O-Et]/PS.[2′-OH]/PS.[2′-O-Et]/PS oligoribonucleotide

[0309] In the manner of Example 8 a chimeric compound having 2′-O-ethylnucleosides in its “wing” segments, 2′-OH nucleosides in its “gap”segment and phosphorothioate linkages throughout is prepared.

[0310] ii. Chimeric 2′-O-propyl oligoribonucleotide, e.g.,[2′-O-Pr]/PS.[2′-OH]/PS.[2′-O-Pr]/PS oligoribonucleotide

[0311] In the manner of Example 8 a chimeric compound having 2′-O-propylnucleosides in its “wing” segments, 2′-OH nucleosides in its “gap”segment and phosphorothioate linkages throughout is prepared.

[0312] iii. [2′-O-F]/PS.[2′-OH]/PS.[2′-O-F]/PS oligoribonucleotide

[0313] In the manner of Example 8 a chimeric compound having 2′-fluoronucleosides in its “wings” segments, 2′-OH nucleosides in its “gap”segment and phosphorothioate linkages throughout is prepared.

[0314] iv. [2′-O-EtOMe]/PS.[2′-OH]/PS.[2′-O-EtOMe]/PSoligoribonucleotide

[0315] In the manner of Example 8 a chimeric compound having2′-O-methoxyethyl nucleosides in its “wings” segments, 2′-OH nucleosidesin its “gap” segment and phosphorothioate linkages through out isprepared.

[0316] v. [2′-O-EtOMe]/PS.[2′-OH]/PS.[2′-F]/PS oligoribonucleotide

[0317] In the manner of Example 8 a chimeric compound having2′-O-methoxyethyl nucleosides in its 5′ “wing” segment, 2′-OHnucleosides in its “gap” segment, 2′-fluoro nucleosides in its 3′ “wing”segment, and phosphorothioate linkages through out is prepared.

[0318] vi. [2′-O-EtOMe]/PS.[2′-OH]/PS.[2′-O-Me]/PS oligoribonucleotide

[0319] In the manner of Example 8, a chimeric compound having2′-O-methoxyethyl nucleosides in its 5′ “wing” segment, 2′-OHnucleosides in its gap, 2′-O-methyl nucleosides in its 3′ “wing” segmentand phosphorothioate linkages through out is prepared.

EXAMPLE 14

[0320] Chimeric Oligoribonucleotides having Variable Backbone Linkagesand Variable Nucleosides

[0321] i. [2′-O-Me]/PMe.[2′-OH]/PS.[2′-F]/PS oligoribonucleotide

[0322] In the manner of Example 8 using chemistries of Example 6, achimeric compound having 2′-O-methyl nucleosides in its 5′ “wing”segment, 2′-OH nucleosides in its “gap,” 2′-O-fluoro nucleosides in its3′ “wing” segment, phosphorothioate linkages in the “gap” segment andthe 3′ “wing” segment and methyl phosphonate linkages in the 5′ “wing”segment is prepared.

[0323] ii. [2′-O-Me]/PME.[2′-OH]/PS.[2′-Pr]/PI oligoribonucleotide

[0324] In the manner of Example 8 using chemistries of Example 6, achimeric compound having 2′-O-methyl nucleosides in its 5′ “wing”segment, 2′-OH nucleosides in its “gap,” 2′-O-propyl nucleosides in its3′ “wing” segment, phosphorothioate linkages in the “gap” segment,methyl phosphonate linkages in 5′ “wing” segment and phosphinatelinkages in the 3′ “wing” segment is prepared.

EXAMPLE 15

[0325] Chimeric Oligoribonucleotides that Include Surrogate Nucleosides

[0326] i. Morpholino nucleoside surrogate containingoligoribonucleotide, e.g., [morpholino nucleosidesurrogate].[2′-OH]/PS.[morpholino nucleosidesurrogate]oligoribonucleotide

[0327] In the manner of Examples 7 and 8, a chimeric compound havingmorpholino nucleosides prepared as per the teachings of U.S. Pat. No.5,506,337 in its “wing” segments and 2′-OH nucleosides linked viaphosphorothioate linkages in its “gap” segment is prepared.

[0328] ii. Cyclobutyl nucleoside surrogate containingoligoribonucleotide, e.g., [cyclobutyl nucleosidesurrogate]/PS.[2′-OH]/PS.[cyclobutyl nucleoside surrogate]/PSoligoribonucleotide

[0329] In the manner of Examples 7 and 8, a chimeric compound havingcyclobutyl surrogate nucleosides prepared as per the teachings of U.S.Pat. No. 5,359,044 in its “wing” segments, 2′-OH nucleosides in its“gap” segment and phosphorothioate linkages through out is prepared.

[0330] iii. Pyrrolidine nucleoside surrogate containingoligoribonucleotide, e.g., [pyrrolidine nucleosidesurrogate]/PS.[2′-OH]/PS.[pyrrolidine sugar]/PS oligoribonucleotide

[0331] In the manner of Examples 7 and 8, a chimeric compound havingpyrrolidine surrogate nucleosides prepared as per the teachings of U.S.Pat. No. 5,519,135 in its “wing” segments, 2′-OH nucleosides in its“gap” segment and phosphorothioate linkages through out is prepared.

[0332] iv. “3′-End” gapped PNA.phosphorothioate chimera, e.g.PNA.[2′-OH]/PS oligoribonucleotide

[0333] In the manner of Example 8 in combination with the chemistry ofExamples 7-b, a chimeric compound having an “open gap” at its 3′terminus” formed from 2′-OH nucleosides having phosphorothioate linkagesand PNA surrogate nucleosides in the 5′ “wing” segment, is prepared.

EXAMPLE 16

[0334] Chimeric Oligoribonucleotides that Include Nucleosides havingModified Bases

[0335] i. N-2 modified purine containing oligoribonucleotide, e.g.,[Mod-purine]/PS.[2′-OH]/PS.[Mod-purine]/PS oligoribonucleotide

[0336] In the manner of Example 8, a chimeric compound having4,7,10,13-tetraazahexadec-1-yl guanosine nucleosides prepared as per theteachings of U.S. Pat. No. 5,459,255 in its “wing” segments, 2′-OHnucleosides in its “gap” and phosphorothioate linkages through out isprepared.

[0337] ii. C-5 modified pyrimidine containing oligoribonucleotide, e.g.,[Mod-pyr]/PS.[2′-OH]/PS.[Mod-pyr]/PS oligoribonucleotide

[0338] In the manner of Example 8, a chimeric compound having 5-propynylpyrimidine nucleosides prepared as per the teachings of U.S. Pat. No.5,484,908 in its “wing” segments, 2′-OH nucleosides in its “gap” segmentand phosphorothioate linkages through out is prepared.

[0339] iii. N-2, C-6 modified purine containing oligoribonucleotide,e.g., [Mod-purine]/PS.[2′-OH)/PS.[Mod-purine]/PS oligoribonucleotide

[0340] In the manner of Example 8, a chimeric compound having6-hydroxy-2-fluoro purine nucleosides prepared as per the teachings ofU.S. Pat. No. 5,459,255 in its “wing” segments, 2′-OH nucleosides in its“gap” and phosphorothioate linkages through out is prepared.

[0341] iv. 2′-O-alkyl, C-5 modified pyrimidine containingoligoribonucleotide, e.g.,[2′-O-Propyl-Mod-pyr]/PS.[2′-OH]/PS-[2′-O-propyl-Mod-pyr]/PSoligoribonucleotide

[0342] In the manner of Example 8, a chimeric compound having2′-O-propyl-5-methyl cytidine nucleosides in its “wing” segments, 2′-OHnucleosides in its “gap” segment and phosphorothioate linkages throughout is prepared.

[0343] v. 2′-O-alkyl, N-2,C-5 modified pyrimidine containingoligoribonucleotide, e.g.,[2′-O-propyl-Mod-pyr]/PS.[2′-OH]/PS-[2′-O-propyl-Mod-pyr]/PSoligoribonucleotide

[0344] In the manner of Example 8, a chimeric compound having2′-O-propyl-2-thio-5-methyl uridine nucleosides in its “wing” segments,2′-OH nucleosides in its “gap” segment and phosphorothioate linkagesthrough out is prepared.

[0345] vi. 2′-O-aminoalkyl, N-2,C-5 modified pyrimidine containingoligoribonucleotide, e.g., [2′-O-aminopropyl-Mod-pyr]/PS[2′-OH]/PS.[2′-O-aminopropyl-Mod-pyr]/PS oligoribonucleotide

[0346] In the manner of Example 8, a chimeric compound having2′-O-aminopropyl-2-thio-5-methyl uridine nucleosides in its “wing”segments, 2′-OH nucleosides in its “gap” segment and phosphorothioatelinkages through out is prepared.

[0347] vii. 2′-O-fluoro, N-2, C-5 modified pyrimidine containingoligoribonucleotide, e.g.,[2′-O-fluoro-Mod-pyr]/PS.[2′-OH]/PS-[2′-O-fluoro-Mod-pyr]/PSoligoribonucleotide

[0348] In the manner of Example 8, a chimeric compound having2′-O-fluoro-2-thio-5-methyl uridine nucleosides in its “wing” segments,2′-OH nucleosides in its “gap” segment and phosphorothioate linkagesthrough out is prepared.

EXAMPLE 17

[0349] Cell Culture and Northern Blot Analysis of Ras Target

[0350] T24 cells were maintained as monolayers in McCoys medium(GIBCO-BRL, Gaithersburg, Md.) supplemented with 10% fetal bovine serumand 100 units/ml penicillin. After treatment with oligomeric compoundsfor 24 hrs the cells were trypsinzed, centrifuged and total cellular RNAwas isolated according to standard protocols (see Ausubel et al.,Current Protocols in Molecular Biology, 1988, Wiley and Sons, New York,N.Y.). To quantify the relative abundance of Ha-ras mRNA, total RNA (10ug) was transferred by northern blotting onto Bio-Rad Zeta probemembrane (Bio-Rad, Hercules, Calif.) and UV crosslinked (Stratalinker™,Stratagene, LaJolla, Calif.). Membrane bound RNA was hybridized to a ³²plabeled 0.9 kb Ha-ras cDNA probe (Oncogene Science, Pasadena, Calif.)and exposure to XAR film (Kodak, Rochester, N.Y.). The relative amountof Ha-ras signal was determined by normalizing the Ha-ras signal to thatobtained when the same membrane was stripped and hybridized with a probefor human glyceraldehyde 3-phosphate dehydrogenase (G3PDH, Clontech,Palo Alto, Calif.). Signals from northern blots were quantified usingphosphoimager and image quant software (Molecular Dynamics, Sunnyvale,Calif.).

EXAMPLE 18

[0351] Compound Treatment of Cells

[0352] Cells growing in monolayer were washed once with warm PBS thenOpti-MEM (GIBCO-BRL) medium containing Lipofectin (GIBCO-BRL) at aconcentration of 5 ug/ml per 200 nM of oligo with a maximumconcentration of 15 ug/ml was added. Oligomeric compounds were added andincubated at 37° C. for 4 hrs when the medium was replaced with fullserum medium. After 24 hrs in the presence of the compound the cellswere harvested and RNA prepared for further analysis.

EXAMPLE 19

[0353] RNase H Analysis

[0354] RNase H analysis was performed using 17 base oligoribonucleotidescorresponding to bases (+23 to +47) of activated (codon 12 mutation)Ha-ras mRNA. 5′ End labeled RNA (20 nM) was incubated with a 100-foldmolar excess of the various test oligoribonucleotides in a reactioncontaining 20 mM Tris-Cl, pH 7.5, 100 mM KCl, 10 mM MgCL₂, 1 mMdithiothreitol, and 4 units of RNase inhibitor (Pharmacia, Newark, N.J.)in a final volume of 100 ul. The oligoribonucleotides were melted byheating to 95° C. for 5 minutes then allowed to cool slowly to roomtemperature in 2 liters bath of water 90° C. Duplex formation wasconfirmed by the shift in mobility between the single stranded endlabeled sense RNA and the annealed duplex on non denaturingpolyacrylamide gels. The resulting duplexes were tested as substratesfor digestion by E. coli RNase H (USB, Cleveland, Ohio). 1 μl of a1×10⁻⁹ mg/ml solution of RNase H was added to 10 μl of the duplexreaction incubated at 370° C. for 30 minutes, the reaction wasterminated by the addition of denaturing loading buffer and reactionproducts were resolved on a 12% polyacrylamide gel containing 7 M Ureaand exposed to XAR film (Kodak).

EXAMPLE 20

[0355] Cell Free in vitro Nuclease Assay

[0356] Duplexes used in the cell free T24 extract experiments wereannealed as described above with the exception that after formation ofthe duplex, the reaction was treated with 1 μl of a mixture RNase T andA (Ambion RPAII kit, Austin, Tex.) and incubated for 15 min at 37° C.,and then gel purified from a nondenaturing 12% polyacrylamide gel. T24cell nuclear and cytosolic fractions were isolated as describedpreviously (Szyf, M., Bozovic, V., and Tanigawa, G., J. Biol. Chem.,1991, 266, 10027-10030). Annealed duplexes (10 μl) were incubated with 3μg of the T24 cytosolic extract at 37° C. The reaction was terminated byphenol/chloroform extraction and ethanol precipitated with the additionof 10 μg of tRNA as a carrier. Pellets were resuspended in 10 μl ofdenaturing loading dye, products were resolved on 12% denaturingacrylamide gels as described above. ³²P-labeled 17-base RNA washydrolysed by heating to 95° C. for 10 mintes in the presence of 50 mMNaCO₃, pH=9.0 to generate a molecular weight ladder.

EXAMPLE 21

[0357] Determination of 5′ and 3′ Termini

[0358] Non-labeled duplex was treated with T24 extracts as donepreviously, half of this reaction was treated with calf intestinalphosphatase (CIP, Stratagene) and half was left untreated. Thephosphatase was inactivated by heating to 95° C. and the reactions wereextracted with phenol/chloroform and then precipitated in ethanol withglycogen as a carrier. The precipitates were then treated with T4polynucleotide kinase (Stratagene) and ³²P-γ-ATP (ICN, Irvine, Calif.).The samples were again extracted by phenol/chloroform and precipitatedwith ethanol, the products of the reaction were then resolved on a 12%acrylamide gel and visualized by exposure to XAR film. The 3′-terminusof the cleaved duplex was evaluated by the reaction of duplex digestionproducts with T4 RNA ligase (Stratagene) and ³²P-pCp (ICN).

EXAMPLE 22

[0359] Chimeric 2′-methoxy Oligoribonucleotides Mediate Digestion ofTarget RNA in T24 Cells

[0360] Structure activity analyses of antisense oligonucleotidesspecific for codon 12 of the Ha-ras oncogene containing various 2′-sugarmodifications were reported by Monia, et al., J. Biol. Chem., 1992, 267,19954-19962 and Monia et al., J. Biol. Chem., 1993, 268, 14514-14522. Inthose reports, although the 2′-modified oligonucleotides hybridized withgreater affinity to RNA than did unmodified 2′-deoxy oligos they werecompletely ineffective in inhibiting Ha-ras gene expression. The lack ofactivity observed with these 2′-modified oligos was directly attributedto their inability to create duplexes that could serve as substrates fordegradation by RNase H. Following a similar protocol, stretches ofribonucleotides were introduced into the center of 17 base 2′-methoxyoligoribonucleotides targeting Ha-ras mRNA to form2′-methoxy-2′-hydorxy-2′-methoxy phosphorothioate oligoribonucleotide“gapped” chimeric compounds that have varying ribonucleotide content inthe central gap segment (see FIG. 1 for a representation of thesecompounds as well as their base sequence). When hybridized to theircellular target the resultant duplex consists of two stretches that arenot targets for nucleolytic degradation (the 2′-methoxy “wings”) and one2′-hydroxyl oligoribonucleotide stretch that was found to be a targetfor a novel ribonuclease activity that recognizes RNA:RNA duplexes. T24human bladder carcinoma cells were used that contain an activating G-Ttransversion mutation in the Ha-ras gene at the codon 12 position. The“gapped” chimeric compounds specific for this mutation were transfectedinto T24 cells growing in culture. After incubation with the compoundsfor 24 hrs, cells were harvested, total cytosolic RNA isolated andNorthern blot analysis for Ha-ras mRNA levels performed. Fully modified2′-methoxy oligonucleotides did not support nucleolytic cleavage oftarget mRNA and therefore did not lead to a reduction in steady statelevels of Ha-ras mRNA even at the highest concentration tested (FIGS. 2Aand 2B). An RNA gapmer oligonucleotide with only 3 ribonucleotides inthe gap was also incapable of inducing nucleolytic cleavage of thetarget RNA (FIGS. 2C and 2D). However, T24 cells treated with RNA gapmeroligonucleotides containing 5, 7 and 9 ribonucleotides in the gap aswell as a full phosphorothioate oligoribonucleotide molecule alldisplayed dose dependent reductions in Ha-ras steady state mRNA levels(FIGS. 3B-3D). T24 cells treated with a control 9 RNA gapmeroligonucleotide that contained four mismatched bases in its sequence didnot show dose dependent reduction in Ha-ras mRNA suggesting thathybridization to the target RNA is essential for activity (FIG. 3E). TheRNA gapmer compounds showed dose dependent inhibition of Ha-ras steadystate mRNA levels.

[0361] The ability,of the RNA gapmer compounds to reduce Ha-ras mRNA wasdependent on the size of the RNA gap and thus the size of the RNA:RNAduplex formed in vivo. Treatment of cells with the 3 base RNA gapmercompounds resulted in no cleavage of the target whereas the 5, 7 and 9base RNA gapmer compounds resulted in reduction in Ha-ras mRNA (FIG. 4).The fact that the RNA gapmer oligonucleotide containing 3ribonucleotides in the gap was unable to induce reduction in target mRNAsuggests that the activity involved requires a minimal RNA:RNA duplexregion of at least four ribonucleotides for binding and cleavage of thetarget. Interestingly, chimeric DNA gapmer oligonucleotides that containdeoxynucleotides in the gap instead of ribonucleotides show the sameminimal gap size requirements to form substrates for RNase H mediateddegradation of the target mRNA (Crooke et al., Annu. Rev. Pharmacol.,1996, 36, 107), suggesting that RNase H and the double stranded RNaseactivity described here may share some properties, although theirsubstrates are clearly different.

[0362] A control 9 RNA gapmer compound that contains four mismatchedbases in its sequence resulted in essentially no reduction in Ha-rasmRNA as expected as is shown in FIG. 3E. A full phosphorothioateoligoribonucleotide molecule had approximately the same activity as the5 RNA gapmer oligo (FIG. 3D). This might have been due to the relativedecrease in stability of the full oligoribonucleotide in vivo resultingfrom inactivation by single stranded ribonucleases, as 2′-methoxyphosphorothioate oligodeoxynucleotides are considerably more stable thanphosphorothioate oligoribonucleotides. Crooke et al., J. Pharmacol Exp.Ther., 1996, 277, 923-937. Treatment of T24 cells with the variousoligonucleotides and various concentrations up to 800 nM was done intriplicate and quantification of Ha-ras mRNA levels indicate that at 600nM the 5 gapmer reduces Ha-ras mRNA by 51%, the 7 gapmer by 49%, the 9gapmer by 77% and the full ribonucleotide by 38% when compared to nontreated controls. This suggests that RNA gapmer oligoribonucleotidesprotected by 2′-methoxy wings would be more potent molecules. As shownin this example, an endoribonuclease activity in T24 human bladdercarcinoma cells recognizes the internal RNA:oligoribonucleotide portionof a chimeric duplex and reduced the target MRNA levels.

EXAMPLE 23

[0363] An Activity Present in T24 Cellular Extracts Induces Cleavage ofGapmer Oligoribonucleotide:RNA Duplex within the Internal RNA:RNAPortion in vitro

[0364] To further characterize the double-stranded RNA cleavage activityin T24 cells, T24 cellular extracts were prepared and tested for theability to cleave the 9 gap oligoribonucleotide:RNA duplex in vitro. The9 gap compound:³²P-end labeled RNA duplex was incubated with 3 μg ofcytosolic extract at 37° C. for varying time periods as shown in FIG. 4,followed by phenol chloroform extraction ethanol precipitation andseparation of the products on a denaturing gel. That this duplex was asubstrate for digestion by an activity present in T24 extracts is shownby the loss of full length end labeled RNA and the appearance of lowermolecular weight digestion products indicated by arrows in FIG. 4. Inaddition, the activity responsible for the cleavage of the duplex hasspecificity for the RNA:RNA portion of the duplex molecule, as indicatedby the sizes of the cleavage products it produces (see the physical mapof the ³²P-end labeled RNA, far right in FIG. 4. RNase H cleavage of a 9deoxynucleotide gap oligonucleotide:RNA duplex and cleavage of the 9ribonucleotide gap oligoribo-nucleotide:RNA duplex by T24 cellularextracts appears to result in similar digestion products. This is seenby comparing the gels of FIGS. 4 and 5. Both activities. displayedpreferred cleavage sites near the 3′ end of the target RNA in theirrespective duplexes which suggests that they may share binding as wellas mechanistic properties. Cellular extracts prepared from humanumbilical vein epithelial cells (HUVEC), human lung carcinoma (A549) andHela cell lines all contained an activity able to induce cleavage of the9 RNA gapmer:RNA target duplex in vitro.

EXAMPLE 24

[0365] Cleavage of Target RNA in both Cytoplasmic and Nuclear Fractionsof Cell Products

[0366] The cellular distribution of the double stranded RNase activitydescribed herein was further evaluated. Nuclear extracts were preparedfrom T24 cells and tested for the ability to digest the 9 RNA gapmeroligonucleotide:RNA duplex. Nuclear extracts prepared from T24 cellswere able to degrade the target duplex, and the activity was found to bepresent in the nuclear fraction at comparable levels to that in thecytoplasmic fractions.

[0367] An RNA gapmer oligonucleotide was synthesized that containedphosphorothioate linkages throughout the entire length of the molecule.Since this results in increased stability to single stranded nucleases,it was reasoned that it would inhibit cleavage of the antisense strandby the dsRNase as well. Therefore, to determine if the activitydescribed above can cleave both strands in a RNA duplex molecule, a 9RNA gapmer antisense oligonucleotide that contained phosphorothioatelinkages in the wings between the 2′ methoxy nucleotides but hadphosphodiester linkages between the nine ribonucleotides in the gap wassynthesized. A duplex composed of this ³²P-labeled 9 RNA gapmerphosphodiester/phosphorothioate oligonucleotide and its complementaryoligoribonucleotide was tested as a substrate for double stranded RNaseactivity in T24 extracts. The activity was capable of cleaving theantisense strand of this duplex as well as the sense strand and thepattern of the digestion products indicated that cleavage was againrestricted to the RNA:RNA phosphodiester portion of the duplex.

EXAMPLE 25

[0368] An RNA Gapmer Oligonucleotide:RNA Duplex is not a Substrate forRNase H

[0369] To exclude the possibility that the cleavage shown in Example 23might be due to RNase H, the ability of E. coli RNase H to cleave a 17base pair duplex of the 9 gapmer oligoribonucleotide and itscomplementary 5′ ³²P-labeled RNA in vitro was tested. FIG. 5 shows theexpected shift in electrophoretic mobility when duplexes were formed andanalyzed on a native gel next to the single stranded ³²P-end labeledRNA. As can be seen in FIG. 5 in the far right panel, the 9 Gapmeroligoribonucleotide:RNA duplex was not a substrate for RNase H cleavageas no lower molecular weight bands appeared when it was treated withRNase H. However, as expected a full deoxy oligonucleotide:RNA duplexwas cleaved by RNase H under the same conditions, as is evident by theappearance of lower molecular species in the enzyme treated lane (FIG.5, left panel). A duplex composed of a 9 gapmer DNA oligonucleotide andits complementary RNA was a substrate for RNase H cleavage. The factthat the RNase H cleavage sites in this particular duplex were localizedto the DNA:RNA portions of the duplex further demonstrates that the RNAgapmer oligoribonucleotide:RNA duplex is not a substrate for RNase Hdigestion.

[0370] It is interesting to note that RNase H cleavage of the 9 DNAgapmer oligonucleotide:RNA duplex (FIG. 5, left panel) and cleavage ofthe 9 RNA gapmer oligonucleotide:RNA duplex by T24 cellular extractsresulted in similar digestion products (see FIG. 4). Both RNase H andthe activity in T24 cells displayed the same preferred cleavage sites ontheir respective duplexes. Moreover, at this site, both theoligonucleotides were roughly comparable in potency. Cleavage wasrestricted to the 3′ end of the target RNA in the region opposite eitherthe DNA or RNA gap of the respective antisense molecule.

[0371] While not wishing to be bound by any particular theory, theimmediately preceding result suggests that RNase H and the dsRNase ofthe invention may share binding as well as mechanistic properties.However, analysis of DNA and RNA gapmer oligonucleotides targeting foursites on c-Raf mRNA revealed that RNase H and the dsRNase activitydescribed here clearly have different substrate specificities.“RNA-like” gapmer oligonucleotides targeted to the c-Raf mRNA were notable to induce reduction in mRNA whereas RNase H activeoligodeoxynucleotides targeted to the same site were able to reducetarget mRNA levels. To determine if the lack of cleavage induced by thefour c-Raf “RNA gapmers” in T24 cells was due to possible sequencespecificity or cleavage, the four c-Raf “RNA-like gapmers,” the ras“RNA-like gapmer” and the corresponding “DNA-like gapmers” wereprehybridized to ³²P-labeled target oligoribonucleotides and incubatedwith T24 homogenates. The ras “RNA-like gapmer” supported cleavage ofthe ras target RNA almost as efficiently as the “DNA gapmer.” However,only one of the “RNA-like gapmers” targeted to c-Raf segments (SEQ IDNO: 8) supported any cleavage and the rate of cleavage for the “RNA-likegapmer” was much slower than the comparable “DNA-like gapmer.” Thus, incontrast to RNase H, the dsRNase displays considerable sequencespecificity.

EXAMPLE 26

[0372] Nuclease Activity Generates 5′-phosphate and 3′-hydroxyl Termini

[0373] To determine the nature of the 5′ termini left by nucleasecleavage of the duplex in vitro, non-labeled duplex was incubated withT24 cellular extracts as previously described then reacted with T4polynucleotide kinase and [³²P-γ-ATP] with or without prior treatmentwith calf intestinal phosphatase. Phosphatase treatment of the duplexproducts was seen to be essential for the incorporation of ³²P labelduring the reaction with polynucleotide kinase, indicating the presenceof a phosphate group at the 5′ termini. The 3′ termini were evaluated bythe reaction of duplex digestion products with T4 RNA ligase and³²P-pCp. T4 RNA ligase requires a free 3′-hydroxyl terminus for theligation of ³²P-pCp. The ability of the duplex digestion products toincorporate ³²P-pCp by T4 RNA ligase indicates the presence of3′-hydroxyl groups.

EXAMPLE 27

[0374] Purification and Characterization of Double-StrandedRibonucleases from Mamallian Tissues

[0375] In order to determine if mamallian cells, other than culturedcell lines, contain double-strand RNase activity, and to provide asource from which such ribonucleases might be purified, the followingefforts were undertaken to identify and purify dsRNases from rat liverhomogenates.

EXAMPLE 27-a

[0376] Substrates and Assays for dsRNases

[0377] In preliminary experiments, double-strand RNase activity wasobserved in rat liver homogenates, but the homogenates also displayedhigh levels of single-strand RNases that complicated analysis of thedsRNase activities because of cleavage of the oligoribonucleotideoverhangs after cleavage by the dsRNases. To solve this problem, twoadditional substrates and a non-denaturing gel assay were used. The“sense” strand was an oligoribonucleotide having phosphodiester linkagesin an eight-base gap with flanks having either (a) residues withphosphorothioate linkages or (b) 2′-methoxynucleosides withphosphorothioate linkages. The “antisense” strand in both substratescontained 2′-methoxy phosphorothioate wings on either side of aneight-base ribonucleotide gap having either phosphodiester orphosphorothioate linkages (Table 1). Such dsRNase substrates were morestable to exonuclease digestion than an oligoribonucleotide andsubstrates with both phosphorothioate linkages and 2′-methoxynucleosides was extremely stable. These features are important becauseof the abundance of single-strand RNases relative to the double-strandRNase activity in the rat liver and supported the use of non-denaturingassays. TABLE 1 Artificial Substrates for Mamallian dsRNases* Ha-rasTARGETED SENSE/ANTISENSE OLIGONUCLEOTIDES SEQ ID NO:1 5′-GGG CGC CGU CGGUGU GG-3′ SEQ ID NO:2 3′-CCC GCG GCA GCC ACA CC-5′ C-raf TARGETEDSENSE/ANTISENSE OLGONUCLEOTIDES SEQ ID NO:3 5′-CCG AAU GUG ACC GCC UCCCG-5′ SEQ ID NO:4 3′-GGC UUA CAC UGG CGG AGG GC-3′ SEQ ID NO:5 5′-UCAAUG GAG CAC AUA CAG GG-3′ SEQ ID NO:6 3′-AGU UAC CUC GUG UAU GUC CC-5′SEQ ID NO:7 5′-AAU GCA UGU CAC AGG CGG GA-3′ SEQ ID NO:8 3′-UUA CGU ACAGUG UCC UCC CU-5′

[0378] Both rat liver cytosolic and nuclear extracts induced cleavage ofthe duplex substrate. Both extracts resulted in more rapidly migratingbands on native gel electrophoretic analyses. The cytosoliclextractappeared to be more active than the nuclear extract. A double-strandRNase, RNase V1 (Pharmacia, Piscataway, N.J.) cleaved the substrate; T24extracts also cleaved the substrate. Neither bacterial nor single-strandRNase cleaved the substrate, with the exception of RNase A, which atvery high concentrations resulted in some cleavage. It is unclearwhether that cleavage was due to a contaminating double-strand RNase orif RNase A can, under some conditions, cleave double-strand substrates.

EXAMPLE 27-b

[0379] Purification of dsRNases from Rat Liver Cytosolic and NuclearExtracts

[0380] In order to purify the mammalian dsRNase identified herein, 0.5kg of rat liver was homogenized in Buffer X [10 mM Hepes (ph 7.5), 25 mMKCl, 0.15 mM spermine, 0.5 mM spermidine, 1 mM EDTA, 2 M sucrose, 10%glycerol; all reagents from Sigma Chemical Co., St. Louis, Mo.) andcentrifuged in a Beckman J2-21M centrifuge (Beckman, Fullerton, Calif.)at 10,000 rpm for 1.5 hours. The supernatant was precipitated with 40%ammonium sulfate (Sigma). All the dsRNase activity was recovered in the40% ammonium sulfate precipitate. The pellet was resuspended in Buffer A[20 mM Hepes (ph 6.5), 5 mM EDTA, 1 mM DTT, 0.25 mM phenylmethylsulfonylfluoride (PMSF), 0.1 M KCl, 5% glycerol, 0.1% NP40, 0.1% Triton X-100;all reagents from Sigma] and dialyzed to remove ammonium sulfate.Approximately 40 g of cytosolic extract were obtained from 0.5 kg liver.

[0381] A crude nuclear pellet, prepared as in the previous Examples, wasresuspended and homogenized in Buffer Y [20 mM Hepes (ph 7.5), 0.42 MNaCl, 1.5 mM MgCl₂, 0.2 mM EDTA, 0.5 mM DTT, 0.5 mM PMSF, 25% glycerol].The homogenate was centrifuged in a J2-21M centrifuge (Beckman) at10,000 rpm for 1.5 hrs. The supernatant was precipitated with 70%ammonium sulfate. The pellet was resuspended in Buffer A and dialyzed.All the dsRNase activity was recovered in the 70% ammonium sulfateprecipitate. Approximately 5 g Of nuclear extract were obtained from 0.5kg liver.

[0382] Ion exchange chromatography was then performed in order tofurther purify the dsRNases of the invention. Nuclear and cytosolicextracts in Buffer A were loaded onto Hi-Trap columns (Pharmacia,Piscataway, N.J.) for FPLC. The extracts were eluted with a lineargradient of NaCl and samples were collected. TheWUV absorption at 257 nMof the samples was determined. Samples were centrifuged at 8,000 g for10 minutes, resuspended in Buffer A, concentrated in Ultrafree-15centrifugal filter devices (Millipore, Bedford, Mass.) and analyzed foractivity. The dsRNase activity eluted in fractions corresponding 300-450mM NaCl. In contrast, the dsRNase activity in the nuclear extract elutedat 700-800 mM NaCl.

[0383] Fractions from the ion exchange chromatography were concentratedand subjected to size exclusion chromatography. Active samples from theion exchange chromatography were pooled, applied to a TSK G-3000 column(TosoHaas, Mongomeryville, Pa.) and run with Buffer A containing 100 mMNaCl. Samples (200 to 400 ul) were collected and their UV absorption at257 ηM was determined. Samples were concentrated using Ultrafree-15centrifugal filter devices (Millipore) and then analyzed for activity.

[0384]FIG. 6 shows a polyacrylamide gel electrophoretic analysis of theconcentrated active fractions after the ion-exchange chromatography, andthe fractions from the size exclusion chromatography. The fraction withgreatest dsRNase activity (lane 4, FIG. 6) had a molecular weight rangeof about 50 to about 80 kilodaltons, and a band at approximately 50kilodaltons appeared to be enhanced on 12% polyacrylamide gelelectrophoresis (PAGE) performed using precast gels (Novex, San Diego,Calif.).

[0385] Table 2 provides a summary of the purification and recovery ofdsRNase activities from nuclear and cytosolic liver extracts. TABLE 2Summary of Purification of dsRNases from Rat Liver Homogenates TotalSpecific Purifi- Protein Activity Activity cation Recovery Fraction (mg)(units*) (unit/mg) Factor (%) Cytosolic 30,000 1,020,000 34 1 100extract Ion 991 459,000 463 14 56 Exchange (Pool) Gel 18.4 100,980 5,600165 22 Filtraton

[0386] One unit is defined as the amount of sample required to digest 10fMol dsRNA duplex in 15 minutes at 37° C. under the conditions describedherein.

[0387] Purification of the dsRNase activities from liver nucleii andcytosol suggests that at least two dsRNases with differing propertiesare capable of cleaving double-strand RNA. The nuclear dsRNase eluted athigher NaCl concentrations from the ion exchange column than thecytosolic dsRNase. However, both require Mg⁺⁺ and cleave at severalsites within the oligoribonucleotide gap. Both require a duplexsubstrate and can cleave oligoribonucleotides in a duplex that is madeup of oligoribonucleotide “sense” and a 2′ methoxy phosphorothioatechimeric “antisense” strand when the duplex has phosphorothioate orphosphorothioate-2′ methoxy nucleoside wings.

[0388] Having (1) established a reproducible and activity-specific assayfor, (2) determined several sources of and (3) achieved an adequatedegree of purification of the dsRNases of the invention via the-methodsdescribed above, the dsRNases are further purified by a variety ofmeans. In all instances, the use of organic solvents is avoided as thedsRNases of the invention are unstable in acetonitrile or methanol (seebelow), and the assays described herein are used to evaluate thepresence or absence of the desired dsRNase in a sample. Furtherpurification steps may include, but are not limited to, the followingmeans.

[0389] Several types of heparin columns have been used to purify avariety of ribonucleases. For example, Sepharose columns have beenutilized in the purification of a sequence-specific ribonuclease fromRana catesbeiana (bullfrog) oocytes (Liao, Nucl. Acids Res., 1992, 20,1371), a ribonuclease from Xenopus laevis oocytes (Nitta et al., Biol.Pharm. Bull. (Jpn.), 1993, 16, 353), several ribonucleases from thethermophilic archaebacterium Sulfobus Solfataricus (Fusi et al., Eur. J.Biochem., 1993, 211, 305), and a ribonuclease from human spleen (Yasudaet al., Eur. J. Biochem., 1990, 191, 523).

[0390] Hydrophobic interaction chromatography is a powerful proteinpurification means which depends on strong salting-out salts to increasethe hydrophobic interactions between the desired protein and a ligandtherefor (Narhi et al., Anal. Biochem., 1989, 182, 266). Hydrophobicinteraction columns (HICs) have been used to purify ribonuclease A fromundesired contaminants (Wu et al., Methods in Enzymology, 1996, 270, 27;Wetlaufer et al., J. Chromatography, 1986, 359, 55).

[0391] The dsRNases of the invention may also be further purified byhydroxyapatite chromatography (Kennedy, Methods in Enzymology, 1990,182, 339). Endo- and exo-ribonuclease have been purified fromTrypanosoma brucei using hydroxyapatite chromatography (Gbenle, Exp.Parisitol., 1990, 71, 432; Gbenle, Mol. Biochem. Parasitol., 1985, 15,37).

[0392] RNA affinity columns may also be used to further purify thedsRNases of the invention. In particular, a commercially availabledouble-stranded RNA affinity column (Pharmacia, Piscataway, N.J.) may beused. Alternatively, a column is prepared in which the matrix thereofcomprises one or more of the dsRNase substrates of the invention (fordetails, see the following Example). Due to the relative sequencespecificity of the dsRNase of the present invention, the latter type ofaffinity column may be preferable. In order to prevent degradation ofthe matrix of either type of double-stranded affinity matrix, samplescomprising the dsRNases of the invention are treated in such a manner soas to limit the degradative capacity of the dsRNase withoutsignificantly altering its ability to bind to the double-stranded RNAsubstrate of the matrix. For example, the degradative activity of thedsRNase of the invention is inhibited in solutions lacking availableMg⁺⁺ due to, for example, the addition of appropriate chelating agentssuch as EDTA, or by addition of NaCl to a sample containing suchdsRNases to a final concentration of at least 300 mM (see the followingsubsection).

[0393] Those skilled in the art will recognize that the above means, aswell as others not herein described, will need to be optimized foroptimal efficiency in purifying the dsRNases of the invention. Forexample, the selection of one or more of the above means as a furtherpurification step, and of the order in which such means are applied,will effect the degree of purity and specific activity of the dsRNase sotreated. However, such optimization is believed to be within the skillof the art given that the assays described herein can be readilyutilized by a skilled artisan to determine the effect of furtherpurification steps on the activity of the desired dsRNase. Othertechniques known in the art, such as SDS-PAGE, can be used to determinethe purity of samples subjected to the above purification means.

EXAMPLE 27-c

[0394] Characterization of Purified Mammalian dsRNases

[0395] The effects of various conditions on the dsRNase activity wereevaluated Using the active fractions after ion exchange chromatography.The dsRNase activity was demonstrable in Tris or phosphate buffers fromabout pH 7 to about pH 10. The dsRNase activity was not stable insolution in acetonitrile or methanol. Furthermore, the activity wasinhibited by NaCl; dsRNase activity was inhibited by 30% at 10 mMNaCl, >60% at 100 mM NaCl and 100% at 300 mM NaCl. Heating for fiveminutes at 60° C., 80° C. or 100° C., inactivated the dsRNase. Optimumactivity was seen in the temperature range of about 37° C. to about 42°C. At 25° C., the dsRNase activity was approximately 50% of thatobserved at 37° C. The dsRNase activity was inhibited at 10, 20 and 50mM EDTA, but not at 5 mM, in agreement with its requirement for Mg⁺⁺,and was stable to multiple freeze/thaws.

EXAMPLE 28

[0396] Further Characterization of the dsRNase Cleavage Site usingPurified Rat dsRNase

[0397] The purified dsRNases were used to characterize the site ofcleavage in more detail. Because it was necessary to minimize anysingle-strand cleavage from occurring after endonuclease cleavage andduring handling, particularly after denaturing of the duplex.Consequently, the most stable duplex substrate, i.e., one in which bothstrands of the duplex contained flanking regions comprised of 2′ methoxynucleosides and phosphorothioate linkages was used.

EXAMPLE 28-a

[0398]³²p Labeling of Oligonucleotides

[0399] The sense oligonucleotide was 5′-end labeled with ³²P using[g³²P]ATP, T4 polynucleotide kinase, and standard procedures (Ausubel etal., 1989). The labeled oligonucleotide was purified by electrophoresison 12% denaturing PAGE (Sambrook et al., 1989). The specific activity ofthe labeled oligonucleotide was approximately 5000 cpm/fmol.

EXAMPLE 28-b

[0400] Double-Strand RNA Digestion Assay

[0401] Oligonucleotide duplexes were prepared in 30 uL reaction buffer[20 mM tris-HCl (pH 7.5), 20 mM KCl, 10 mM MgCl₂, 0.1 mM DTT] containing10 nM antisense oligonucleotide and 10⁵ cpm ³²P labeled senseoligonucleotide. Reactions were heated at 90° C. for 5 min and incubatedat 37° C. for 2 h. The oligonucleotide duplexes were incubated in eitherunpurified and semipurified cellular extracts at a total proteinconcentration of 75 ug unpurified cytosolic extract, 60 ug unpurifiednuclear extract, 5 ug ion exchange purified cytosolic fraction, 5 ug ionexchange purified nuclear fraction, or 0.5 ug ion exchange and gelfiltration purified nuclear fraction. Digestion reactions were incubatedat 37° C. for 0-240 min. Following incubation, 10 uL of each reactionwas removed and quenched by addition of denaturing gel loading buffer [5uL 8 M urea, 0.25% xylene cyanole FF, 0.25% bromphenol blue]. Thereactions were heated at 95° C. for 5 min and resolved in a 12%denaturing polyacrylamide gel. The remaining aliquot was quenched in 2uL native gel loading buffer [glycerol, 0.25% xylene cyanole FF. Thereactions were resolved at 10° C. in a 12% native polyacrylamide gelcontaining 44 mM Tris-borate and 1 mM MgCl₂. Gels were analyzed using aMolecular Dynamics Phosphorimager.

[0402]FIG. 7 displays the native gel results. Lane 1 shows the positionat which the untreated ³²P-labeled sense strand migrated in the nativegel, and lane 2 shows “sense” strand RNA treated with 0.02 units RNaseV1. In the remaining lanes, the results of treatment of dsRNAsesubstrates with 0.02 (lane 3) and 0.002 (lane 4) units of RNase V1,unpurified nuclear extract for 0 minutes (lane 5) or 240 minutes (lane6), unpurified nuclear extract for 240 minutes without Mg⁺⁺ (lane 7),unpurified cytosolic extract for 240 minutes (lane 8), ion exchangepurified cytosolic extract for 240 minutes in the presence (lane 9) orabsence (lane 10) of Mg⁺⁺, and ion exchange/gel filtration purifiedcytosolic extract for 240 minutes in the presence (lane 9) or absence(lane 10) of Mg⁺⁺ are shown.

[0403]FIG. 8 shows the results of analysis of products of digestion ofdsRNAse substrates by denaturing polyacrylamide gel electrophoresis.Lane 1 shows “sense” strand RNA treated with 5×10⁻³ units of RNase A,and lane 2 shows “sense” strand RNA treated with 0.02 units RNase V1.The remaining lanes show dsRNAse products treated with 0.02 (lane 3) and0.002 (lane 4) units of RNase V1, with unpurified nuclear extract for 0minutes (lane 5) or 240 minutes (lane 6), with unpurified cytosolicextract for 240 minutes (lane 7), with ion exchange purified cytosolicextract for 240 minutes (lane 8), and with ion exchange/gel filtrationpurified cytosolic extract for 240 minutes (lane 9). Lane 10 is an RNAbase hydrolysis ladder included for sizing purpose. RNase V1 digestionof the single-strand substrate resulted in little degradation (lane 2).RNase V1 digestion of the duplex resulted in degradates reflectingcleavage at several sites within the gap (lanes 3 and 4). In lanes 4-9,the band at the top of the gel demonstrates that even afterdenaturation, some of the duplex remained annealed, reflecting the veryhigh affinity of duplexes comprised to 2′-methoxy nucleosides. Lanes 6-9show that both the nuclear and cytosolic ribonucleases cleaved thetriplex substrate at several sites with the oligoribonucleotide gap andthat the sites of degradation were different from those of RNase V1. Theposition of the degradates in lanes 6-9 is consistent with them beingthe 2′ methoxy phosphorothioate flanking regions (wings).

EXAMPLE 29

[0404] RNA Affinity Columns and Methods of Purifying Ribonucleases

[0405] Techniques for preparing nucleic acid affinity columns are knownin the art (see, e.g., Kadonaga, Methods in Enzymology, 1991, 208, 10).Such affinity columns comprise a matrix comprising a nucleic acidsubstrate for. a desired compound that binds the substrate eithernonspecifically or in a sequence-specific manner. Initially utilized inthe purification of DNA-binding proteins, RNA affinity columns have alsobeen employed to purify RNA-binding proteins and ribonucleases (see,e.g., Prokipcak et al., J. Biol. Chem., 1994, 269, 9261; Dake et al., J.Biol. Chem., 1988, 263, 7691). A matrix comprising one or more dsRNasesubstrates of the invention has the advantage of providing a dsRNAsubstrate that is resistant to the action of single-strandedribonuclease which are prevalent in many tissues and cells. Such amatrix also comprises a suitable solid support and a linker thatprovides a bridge between the solid support and the dsRNasesubstrate(s).

[0406] Suitable solid supports include, but are not limited to, graftpolymers (U.S. Pat. No. 4,908,405 to Bayer and Rapp); polyacrylamide(Fahy et al., Nucl. Acids Res., 1993, 21, 1819); polyacrylmorpholide,polystyrene and derivatized polystyrene resins (Syvanen et al., Nucl.Acids Res., 1988, 16, 11327; U.S. Pat. Nos. 4,373,071 and 4,401,796 toItakura), including amino methyl styrene resins (U.S. Pat. No. 4,507,433to Miller and Ts'O); copolymers of N-vinylpyrrolidone and vinylacetate(Selinger et al., Tetrahedron Letts., 1973, 31, 2911; Selinger et al.,Die Makromolekulare Chemie, 1975, 176, 609; and Selinger, DieMakromolekulare Chemie, 1975, 176, 1611); TEFLON™ (Lohrmann et al., DNA,1984, 3, 122; Duncan et al., Anal. Biochem., 1988, 169, 104); controlledpore glass (Chow et al., Anal. Biochem., 1988, 175, 63); polysaccharidesupports such as agarose (Kadonaga, Methods Enzymol., 1991, 208, 10;Arndt-Jovin et al., Eur. J. Biochem., 1975, 54, 411; Wu et al., Science,1987, 238, 1247; Blank et al., Nucleic Acids Res., 1988, 16, 10283) orcellulose (Goldkorn et al., Nucl. Acids Res., 1986, 14, 9171; Alberts etal., Meth. Enzymol., 1971, 21, 198) or derivatives thereof, e.g.,DEAE-cellulose (Schott, J. Chromatogr., 1975, 115, 461) orphosphocellulose (Siddell, Eur. J. Biochem., 1978, 92, 621; Bunemann etal., Nucl. Acids Res., 1982, 10, 7163; Noyes et al., Cell, 1975, 5, 301;Bunemann et al., Nucl. Acids Res., 1982, 10, 7181); dextran sulfate(Gingeras et al., Nucl. Acids Res., 1987, 15, 5373); polypropylene(Matson et al., Anal. Biochem., 1994, 217, 306); agarose beads (Kadonagaet al., Proc. Natl. Acad. Sci. U.S.A., 1986, 83, 5889); latex particles(Kawaguchi et al., Nucleic Acids Res., 1989, 17, 6229); nylon beads (VanNess et al., Nucl. Acids Res., 1991, 19, 3345); paramagnetic beads(Gabrielson et al., Nucl. Acids Res., 1989, 17, 6253; Lund, et al.,Nucl. Acids Res., 1988, 16, 10861; Day et al., Biochem. J., 1991, 278,735); silica gels (Yashima et al., J. Chromatogr., 1992, 603, 111);derivatized forms of silica gels, polytetrafluoroethylene, cellulose ormetallic oxides (U.S. Pat. No. 4,812,512 to Buendia); and art-recognizedequivalents of any of the preceding solid supports; microtiter plates(Drmanac et al., Science, 1993, 260, 1649); crosslinked copolymers ofN-vinylpyrrolidone, other N-vinyl-lactam monomers and an ethylenicallyunsaturated monomer having at least one amine or amine-displacablefunctionality as disclosed in U.S. Pat. No. 5,391,667. In one set ofpreferred embodiments, polystyrene or long chain alkyl CPG (controlledpore glass) beads are employed. In another set of preferred embodiments,microscopic glass slides are employed (Fodor et al., Science, 1991, 251,767; Maskos et al., Nucleic Acids Research, 1992, 20, 1679; Guo et al.,1994, 22, 5456; Pease et al., Proc. Natl. Acad. Sci. U.S.A., 1994, 91,5022).

[0407] With regard to the linker, a variety of chemical linking groupsor chains may be employed in the matrices of the invention. Any chemicalgroup or chain capable of forming a chemical linkage between the solidsupport and the dsRNase substrate may be employed. A suitable linker hasthe preferred characteristic of non-reactivity with compounds introducedduring the various steps of oligonucleotide synthesis. It will beappreciated by those skilled in the art that the chemical composition ofthe solid support and the dsRNase substrate will influence the choice ofthe linker. Many suitable linkers will comprise a primary amine group ateither or both termini, as many chemical reactions are known in the artfor linking primary amine groups to a variety of other chemical groups;however, other terminal reactive moieties are known and may be used inthe invention. Suitable linkers include, but are not limited to, linkershaving a terminal thiol group for introducing a disulfide linkages tothe solid support (Day et al., Biochem. J., 1991, 278, 735; Zuckermannet al., Nucl. Acids Res., 15, 5305); linkers having a terminalbromoacetyl group for introducing a thiol-bromoacetyl linkage to thesolid support (Fahy et al., Nucl. Acids Res., 1993, 21, 1819); linkershaving a terminal amino group which can be reacted with an activated 5′phosphate of an oligonucleotide (Takeda et al., Tetrahedron Letts.,1983, 24, 245; Smith et al., Nucl. Acids Res., 1985, 13, 2399; Zarytovaet al., Anal. Biochem., 1990, 188, 214); poly(ethyleneimine) (Van Nesset al., Nucl. Acids Res., 1991, 19, 3345); acyl chains (Akashi et al.,Chem. Lett., 1988, 1093; Yashima et al., J. Chromatogr., 1992, 603,111); polyvinyl alcohol (Schott, J. Chromatogr., 1975, 115, 461); alkylchains (Goss et al., J. Chromatogr., 1990, 508, 279); alkylamine chains(Pon et al., BioTechniques, 1988, 6, 768); biotin-avidin orbiotin-streptavidin linkages (Kasher et al., Mol. Cell. Biol., 1986, 6,3117; Chodosh et al., Mol. Cell. Biol., 1986, 6, 4723; Fishell et al.,Methods Enzymol., 1990, 184, 328); and art-recognized equivalents of anyof the preceding linkers. In a preferred embodiment of the invention, ann-aminoalkyl chain is the linker. Methods of determining an appropriate(i.e., providing the optimal degree and specificity of hybridizationbetween the sensor array and the target oligonucleotide) linker lengthare known in the art (see, e.g., Day et al., Biochem. J., 1991, 278,735).

1 9 1 17 RNA Artificial Sequence Oligonucleotide 1 gggcgccguc ggugugg 172 17 RNA Artificial Sequence Oligonucleotide 2 cccgcggcag ccacacc 17 320 RNA Artificial Sequence Oligonucleotide 3 ccgaauguga ccgccucccg 20 420 RNA Artificial Sequence Oligonucleotide 4 ggcuuacacu ggcggagggc 20 520 RNA Artificial Sequence Oligonucleotide 5 ucaauggagc acauacaggg 20 620 RNA Artificial Sequence Oligonucleotide 6 aguuaccucg uguauguccc 20 720 RNA Artificial Sequence Oligonucleotide 7 aaugcauguc acaggcggga 20 820 RNA Artificial Sequence Oligonucleotide 8 uuacguacag uguccgcccu 20 917 RNA Artificial Sequence Oligonucleotide 9 ccacaccgac ggcgccc 17

What is claimed is:
 1. A synthetic oligomeric compound which isspecifically hybridizable with a preselected RNA target and comprises; afirst segment having at least one ribofuranosyl nucleoside subunit whichis modified to improve the binding affinity of said compound to thepreselected RNA target when compared to the binding affinity of anunmodified oligoribonucleotide to the RNA target; and a second segmentcomprising at least four consecutive ribofuranosyl nucleoside subunitshaving 2′-hydroxyl moieties thereon; said nucleoside subunits of saidoligomeric compound being connected by internucleoside linkages whichare modified to stabilize said linkages from degradation as compared tophosphodiester linkages.
 2. The oligomeric compound of claim 1 furthercomprising a third segment comprising at least one ribofuranosylnucleoside subunit which is modified to improve the binding affinity ofsaid compound to the preselected RNA target when compared to the bindingaffinity of an unmodified oligoribonucleotide to the RNA target.
 3. Theoligomeric compound of claim 1 which, when hybridized with said RNAtarget, is capable of activating a double-stranded RNAse enzyme toeffect cleavage of said RNA target.
 4. The oligomeric compound of claim2 wherein said second segment is positioned between said first and saidthird segments.
 5. The oligomeric co:mpound of claim 2 wherein each ofsaid first and third segments comprise at least three subunits.
 6. Theoligomeric compound of claim 2 wherein said second segment comprisesfrom four to twelve nucleoside subunits.
 7. The oligomeric compound ofclaim 6 wherein said second segment comprises from five to ninenucleoside subunits.
 8. The oligomeric compound of claim 2 wherein saidsecond segment has at least five subunits and said first and thirdsegments each have at least three subunits.
 9. The oligomeric compoundof claim 8 wherein said second segment has at least seven nucleosidesubunits.
 10. A synthetic oligomeric compound which is specificallyhybridizable with a preselected RNA target and comprises; a firstsegment having at least one ribofuranosyl nucleoside subunit that ismodified to improve at least one of: pharmacokinetic binding,absorption, distribution or clearance properties of the compound;affinity or specificity of said compound to said target RNA; ormodification of the charge of said compound as compared to unmodifiedcompound; and a second segment comprising at least four consecutiveribofuranosyl nucleoside subunits having 2′-hydroxyl moieties thereon;said nucleoside subunits of said oligomeric compound being connected byinternucleoside linkages which are modified to stabilize said linkagesfrom degradation as compared to phosphodiester linkages.
 11. Theoligomeric compound of claim 10 further comprising a third segmentcomprising at least one ribofuranosyl nucleoside subunit that ismodified to improve at least one of: pharmacokinetic binding,absorption, distribution or clearance properties of the compound;affinity or specificity of said compound to said target RNA; ormodification of the charge of said compound as compared to unmodifiedcompound.
 12. The oligomeric compound of claim 10 which, when hybridizedwith said RNA target, is capable of activating a double-stranded RNAseenzyme to effect cleavage of said RNA target.
 13. The oligomericcompound of claim 11 wherein said second segment is positioned betweensaid first and said third segments.
 14. The oligomeric compound of claim11 wherein each of said first and third segments comprise at least threesubunits.
 15. The oligomeric compound of claim 11 wherein said secondsegment comprises from four to twelve nucleoside subunits.
 16. Theoligomeric compound of claim 15 wherein said second segment comprisesfrom five to nine nucleoside subunits.
 17. The oligomeric compound ofclaim 11 wherein said second segment has at least five subunits and saidfirst and third segments each have at least three subunits.
 18. Theoligomeric compound of claim 17 wherein said second segment has at leastseven nucleoside subunits.
 19. A synthetic oligomeric compound which isspecifically hybridizable with a preselected RNA target comprising; afirst segment having at least one 2′-O—C₁₋₂₀ alkyl, 2′-O-substitutedC₁₋₂₀ alkyl or 2′-fluoro modified ribofuranosyl nucleoside subunit wherethe substitution on said alkyl is amino, hydroxy or C₁₋₁₀ alkyl ethermodification; a second segment comprising at least four consecutiveribofuranosyl nucleoside subunits having 2′-hydroxyl moieties thereon;and said nucleoside subunits of said oligomeric compound being connectedby internucleoside linkages that are stable to degradation as comparedto phosphodiester bonds.
 20. The oligomeric compound of claim 19 furthercomprising a third segment comprising at least one 2′-O—C₁₋₂₀ alkyl,2′-O-substituted C₁₋₂₀ alkyl or 2′-fluoro modified ribofuranosylnucleoside subunit where the substitution on said alkyl is amino,hydroxy or C₁₋₁₀ alkyl ether.
 21. The oligomeric compound of claim 20wherein said second segment is positioned between said first and saidthird segments.
 22. The oligomeric compound of claim 20 wherein each ofsaid first and third segments comprise at least three subunits.
 23. Theoligomeric compound of claim 20 wherein said second segment comprisesfrom four to twelve nucleoside subunits.
 24. The oligomeric compound ofclaim 20 wherein said second segment comprises from five to ninenucleoside subunits.
 25. The oligomeric compound of claim 20 whereinsaid second segment has at least five subunits and said first and thirdsegments each have at least three subunits.
 26. The oligomeric compoundof claim 20 wherein said second segment has at least seven nucleosidesubunits.
 27. The oligomeric compound of claim 19 which, when hybridizedwith said RNA target, is capable of activating a double stranded RNAseenzyme to effect cleavage of said RNA target.
 28. The oligomericcompound of claim 22 wherein each of said ribofuranosyl nucleosidesubunits of said first and said third segments is modified to include a2′-O—C₁₋₂₀ alkyl, 2′-O-substituted C₁₋₂₀ alkyl or 2′-fluoro and whereinthe substitution on said alkyl is amino, hydroxy or C₁₋₁₀ alkyl ether.29. The oligomeric compound of claim 19 wherein at least two of saidnucleoside subunits are connected by a phosphorothioate,3′-deoxy-3′-thio-phosphorothioate, 5′-deoxy-5′-thio-phosphorothioate,phosphorodithioate, phosphoroselenate, 3′-deoxy phosphinate, 5′-deoxyphosphinate, borano phosphate, 3′-deoxy-3′-amino phosphoramidate,5′-deoxy-5′-amino phosphoramidate, hydrogen phosphonate, boranophosphate ester, phosphoramidate, alkyl phosphonate, aryl phosphonate orphosphotriester linkage.
 30. The oligomeric compound of claim 19 whereineach of the nucleoside subunits of said first segment are connected byphosphorothioate, 3′-deoxy-3′-thio-phosphoro-thioate,5′-deoxy-5′-thio-phosphorothioate, phosphorodithioate,phosphoroselenate, 3′-deoxy phosphinate, 5′-deoxy phosphinate, boranophosphate, 3′-deoxy-3′-amino phosphoramidate, 5′-deoxy-5′-aminophosphoramidate, hydrogen phosphonate, borano phosphate ester,phosphoramidate, alkyl phosphonate, aryl phosphonate or phosphotriesterlinkages.
 31. The oligomeric compound of claim 19 wherein each of saidnucleoside subunits of said first segment are connected byphosphorothioate linkages.
 32. The oligomeric compound of claim 19wherein each of said nucleoside subunits of said second segment areconnected by phosphorothioate linkages.
 33. The oligomeric compound ofclaim 20 wherein each of said nucleoside subunits of said third segmentare connected by phosphorothioate, 3′-deoxy-3′-thio-phosphoro-thioate,5′-deoxy-5′-thio-phosphorothioate, phosphorodithioate,phosphoroselenate, 3′-deoxy phosphinate, 5′-deoxy phosphinate, boranophosphate, 3′-deoxy-3′-amino phosphoramidate, 5′-deoxy-5′-aminophosphoramidate, hydrogen phosphonate, borand phosphate ester,phosphoramidate, alkyl phosphonate, aryl phosphonate or phosphotriesterlinkages.
 34. The oligomeric compound of claim 20 wherein each of saidnucleoside subunits of said third segment are connected byphosphorothioate linkages.
 35. The oligomeric compound of claim 20wherein each of said nucleoside subunits of said first, said second andsaid third subunits are connected by phosphorothioate linkages.
 36. Theoligomeric compound of claim 19 wherein each of the nucleoside subunitsof said first segment are connected by carbonate, carbamate, silyl,sulfur, sulfonate, sulfonamide, formacetal, thioformacetal, oxime,methyleneimino, methylenemethylimino, methylenehydrazo,methylenedimethylhydrazo, methyleneoxymethylimino ormethylenecarbonylamino linkages.
 37. The oligomeric compound of claim 20wherein each of the nucleoside subunits of said third segment areconnected by carbonate, carbamate, silyl, sulfur, sulfonate,sulfonamide, formacetal, thioformacetal, oxime, methyleneimino,methylenemethylimino, methylenehydrazo, methylenedimethylhydrazo,methyleneoxymethylimino or methylenecarbonylamino linkages.
 38. Asynthetic oligomeric compound which is specifically hybridizable with apreselected RNA comprising at least twelve ribofuranosyl.nucleosides ina sequence; said nucleoside subunits being joined by internucleosidebonds which are more stable to degradation as compared to phosphodiesterbonds; the compound having two wing portions interspaced by a gapportion; the wing portions each comprising at least one modifiednucleoside subunit, which modified nucleoside subunit is modified toimprove at least one of: pharmacokinetic binding, absorption,distribution or clearance properties of the compound; affinity orspecificity of said compound to said target RNA; or modification of thecharge of said compound as compared to unmodified compound; the gapportion having at least four consecutive ribonucleoside subunits. 39.The oligomeric compound of claim 38 wherein said gap portion has atleast five consecutive ribonucleoside subunits.
 40. A syntheticoligomeric compound comprising, in sequence; a first segment having aplurality of 2′-O-alkyl nucleoside subunits; a second segment having atleast four consecutive 2′-hydroxyl ribonucleoside subunits; and a thirdsegment having a plurality of 2′-O-alkyl nucleoside subunits; and thenucleoside subunits of the oligomer being joined by phosphorothioateinternucleoside linkages.
 41. The oligomeric compound of claim 40wherein said second segment has at least five consecutive 2′-hydroxylribonucleotide subunits.
 42. The oligomeric compound of claim 40 whereinsaid oligomer is specifically hybridizable with a preselected RNA.
 43. Amethod for specifically cleaving a preselected RNA comprising contactingsaid RNA with an oligomeric compound comprising at least twelveribofuranosyl nucleosides subunits in a sequence which is specificallyhybridizable with said preselected RNA; said nucleoside subunits beingjoined by internucleoside bonds which are more stable to degradation ascompared to phosphodiester bonds; the compound having at least onesegment comprising at least one modified nucleoside subunit, whichmodified nucleoside subunit is modified to improve at least one of:pharmacokinetic binding, absorption, distribution or clearanceproperties of the compound; affinity or specificity of said compound tosaid target RNA; or modification of the charge of said compound ascompared to an unmodified compound; said compound having a furthersegment having at least four consecutive 2′-hydroxyl ribonucleosidesubunits.
 44. The method of claim 43 wherein said further segment has atleast five consecutive ribonucleoside subunits.
 45. A method fortreating an organism having a disease characterized by the undesiredproduction of a protein comprising contacting the organism with anoligomeric compound of the invention having a sequence of nucleosidesubunits capable of specifically hybridizing with a complementary strandof ribonucleic acid with at least one of the nucleoside subunits beingmodified to improve at least one of: pharmacokinetic binding,absorption, distribution or clearance properties of the compound;affinity or specificity of said compound to said target RNA; ormodification of the charge of said compound as compared to unmodifiedcompound; a plurality of the nucleoside subunits being located in aconsecutive sequence and having 2′-hydroxyl-pentofuranosyl sugarmoieties.
 46. A compositions including a pharmaceutically effectiveamount of an oligomeric compound in a pharmaceutically acceptablediluent or carrier, said oligomeric compound comprising a sequence ofnucleoside subunits capable of specifically hybridizing with acomplementary strand of RNA wherein a plurality of the nucleosidesubunits of the oligomeric compound are modified to improve at least oneof: pharmacokinetic binding, absorption, distribution or clearanceproperties of the compound; affinity or specificity of said compound tosaid target RNA; or modification of the charge of said compound ascompared to an unmodified compound; wherein a further plurality of thenucleoside subunits have 2′-hydroxyl-pentofuranosyl sugar moieties. 47.A method for in vitro modification of a sequence-specific target RNAcomprising contacting a test solution containing a dsRNase enzyme andsaid target RNA with an oligomeric compound having a sequence ofnucleoside subunits capable of specifically hybridizing to said targetRNA where at least one of the nucleoside subunits is modified to improvethe affinity or specificity of said compound to said target RNA; andwhere a plurality of the nucleoside subunits have2′-hydroxyl-pentofuranosyl sugar moieties.
 48. A method of concurrentlyenhancing hybridization and dsRNase enzyme activation in an organismcomprising contacting the organism with an oligomeric compound having asequence of nucleoside subunits capable of specifically hybridizing to acomplementary strand of target RNA, where at least one of the nucleosidesubunits is modified to improve at least one of: pharmacokineticbinding, absorption, distribution or clearance properties of thecompound; affinity or specificity of said compound to said target RNA;or modification of the charge of said compound as compared to unmodifiedcompound; wherein a plurality of the nucleoside subunits have2′-hydroxy-pentofuranosyl sugar moieties.
 49. A synthetic oligomericcompound which is specifically hybridizable with a preselected RNAtarget comprising; a first segment including at least one surrogatenucleoside subunit; a second segment comprising at least fourribofuranosyl nucleoside subunits located in a consecutive sequence andhaving 2′-hydroxyl moieties thereon; and said nucleoside subunits ofsaid oligomeric compound being connected by internucleoside linkagesthat are stable to degradation as compared to phosphodiester bonds. 50.The oligomeric compound of claim 49 wherein said surrogate nucleosidesubunit is a peptide nucleic acid subunit.
 51. The oligomeric compoundof claim 49 wherein said surrogate nucleoside subunit is a morpholinonucleoside subunit.
 52. The oligomeric compound of claim of 49 whereinsaid surrogate nucleoside is a cyclobutyl nucleoside.
 53. The oligomericcompound of claim 49 wherein said surrogate nucleoside is a pyrrolidinenucleoside.
 54. A synthetic oligomeric compound which is specificallyhybridizable with a preselected RNA target comprising; a first segmentincluding at least two nucleoside subunits; said nucleoside subunits ofsaid first segment being connected by non-phosphorus internucleosidelinkages; a second segment comprising at least four consecutiveribofuranosyl nucleoside subunits having 2′-hydroxyl moieties thereon;and said nucleoside subunits of said second segment being connected byinternucleoside linkages that are stable to degradation as compared tophosphodiester bonds.
 55. The oligomeric compound of claim 54 whereinsaid non-phosphorous linkages are carbonate, carbamate, silyl, sulfur,sulfonate, sulfonamide, formacetal, thioformacetal, oxime,methyleneimino, methylenemethylimino, methylenehydrazo,methylenedimethylhydrazo or methyleneoxymethylimino,methylenecarbonylamino internucleoside linkages.
 56. The oligomericcompound of claim 54 wherein said non-phosphorus internucleosidelinkages are formacetal, thioformacetal, methylenemethylimino,methylenedimethylhydrazo, methyleneoxymethylimino ormethylenecarbonylamino internucleoside linkages.
 57. The oligomericcompound of claim 54 said nucleoside subunits of said second segmentbeing connected by phosphoro-thioate internucleoside linkages.
 58. Asynthetic oligomeric compound which is specifically hybridizable with apreselected RNA target comprising; a first segment including at leastthree nucleoside subunits; said nucleoside subunits of said firstsegment being connected by alternating phosphorus, non-phosphorusinternucleoside linkages; a second segment comprising at least fourconsecutive ribofuranosyl nucleoside subunits having 2′-hydroxylmoieties thereon; and said nucleoside subunits of said second segmentbeing connected by internucleoside linkages that are more stable todegradation as compared to phosphodiester bonds.
 59. The oligomericcompound of claim 58 wherein said non-phosphorous linkages arecarbonate, carbamate, silyl, sulfur, sulfonate, sulfonamide, formacetal,thioformacetal, oxime, methyleneimino, methylenemethylimino,methylenehydrazo, methylenedimethylhydrazo or methyleneoxymethylimino,methylenecarbonylamino internucleoside linkages.
 60. The oligomericcompound of claim 58 wherein said non-phosphorus internucleosidelinkages are formacetal, thioformacetal, methylenemethylimino,methylenedimethylhydrazo, methyleneoxymethylimino ormethylenecarbonylamino internucleoside linkages.
 61. The oligomericcompound of claim 58 wherein said nucleoside subunits of said secondsegment are connected by phosphorothioate internucleoside linkages. 62.A synthetic oligomeric compound which is specifically hybridizable witha preselected RNA target comprising; a first segment including at leasttwo nucleoside subunits; said nucleoside subunits of said first segmentbeing connected by 3′-deoxy-3′-thio-phosphorothioate,5′-deoxy-5′-thio-phosphorothioate, phosphorodithioate,phosphoroselenate, 3′-deoxy phosphinate, 5′-deoxy phosphinate, boranophosphate, 3′-deoxy-3′-amino phosphoramidate, 5′-deoxy-5′-aminophosphoramidate, hydrogen phosphonate, borano phosphate ester,phosphoramidate, alkyl phosphonate, aryl phosphonate or phosphotriesterphosphate linkages; and a second segment comprising at least fourconsecutive ribofuranosyl nucleoside subunits having 2′-hydroxylmoieties thereon; and said nucleoside subunits of said second segmentbeing connected by internucleoside linkages that are more stable todegradation as compared to phosphodiester bonds.
 63. The oligomericcompound of claim 62 including a third segment of at least twonucleoside subunits, said nucleoside subunits of said third segmentconnected by 3′-deoxy-3′-thio-phosphorothioate,5′-deoxy-5′-thio-phosphoro-thioate, phosphorodithioate,phosphoroselenate, 3′-deoxy phosphinate, 5′-deoxy phosphinate, boranophosphate, 3′-deoxy-3′-amino phosphoramidate, 5′-deoxy-5′-aminophosphoramidate, hydrogen phosphonate, borano phosphate ester,phosphoramidate, alkyl phosphonate, aryl phosphonate or phosphotriesterphosphate linkages.
 64. The oligomeric compound of claim 62 wherein saidnucleoside subunits of said first and third segments are connected byphosphorodithioate, phosphoroselenate, 3′-deoxy phosphinate,3′-deoxy-3′-amino phosphoramidate, phosphoramidate, alkyl phosphonate,aryl phosphonate or phosphotriester phosphate linkages.
 65. A syntheticoligomeric compound which is specifically hybridizable with apreselected RNA target and comprises; a first segment having at leastone ribofuranosyl nucleoside subunit that is not a DNA or RNA majorbuilding block nucleoside; a second segment comprising at least fourconsecutive ribofuranosyl nucleoside subunits having 2′-hydroxylmoieties thereon; said nucleoside subunits of said oligomeric compoundbeing connected by internucleoside linkages which are modified tostabilize said linkages from degradation as compared to phosphodiesterlinkages.
 66. The compound of claim 65 wherein said first segmentnucleoside subunit is selected from nucleosides having xanthine,hypoxanthine, 2-aminoadenine, 6-alkyl derivatives of adenine andguanine, 2-alkyl derivatives of adenine and guanine, 7-alkyl derivativesof adenine and guanine, 5-halouracil and cytosine, 5-propynyl uracil andcytosine, 6-azo uracil, cytosine and thymine, 5-uracil (pseudouracil),4-thiouracil, 2 thio uracil and cytosine, 8-halo, amino, thiol,thioalkyl, hydroxyl adenine and guanine, and 5-trifluoromethyl uraciland cytosine, as their heterocyclic base.
 67. A synthetic oligomericcompound which is specifically hybridizable with a preselected RNAtarget and comprises; a first segment having at least one ribofuranosylnucleoside subunit excluding the nucleoside group consisting ofadenosine, 2′-deoxyadenosine, guanosine, 2′-deoxyguanosine, cytidine,2′-deoxycytidine, uridine and 2′-deoxythymidine; a second segmentcomprising at least four consecutive ribofuranosyl nucleoside subunitshaving 2′-hydroxyl moieties thereon; said nucleoside subunits of saidoligomeric compound being connected by internucleoside linkages whichare modified to stabilize said linkages from degradation as compared tophosphodiester linkages.
 68. A mammalian ribonuclease having theactivity of catalyzing the degradation of a double stranded substratewherein one of said strands of said substrate is a mRNA and the other ofsaid strands of said substrate comprises a compound having in sequence afirst segment comprising a plurality of 2′ modified nucleoside subunitsand a second segment comprising at least four consecutive ribofuranosylnucleoside subunits having 2′-hydroxyl moieties thereon.
 69. A mammalianribonuclease of claim 68 wherein said subunits of said compound arejoined by phosphorothioate internucleoside linkages or phosphodiesterinternucleoside linkages.
 70. A mammalian ribonuclease of claim 68wherein said subunits of said first segment of said compound are joinedby phosphorothioate internucleoside linkages.
 71. A mammalianribonuclease of claim 70 wherein said subunits of said second segment ofsaid compound are joined by phosphodiester internucleoside linkages. 72.A mammalian ribonuclease of claim 70 wherein said subunits of saidsecond segment of said compound are joined by phosphorothioateinternucleoside linkages.
 73. A mammalian ribonuclease of claim 68wherein said subunits of said first segment of said compound are2′-O-alkyl nucleoside subunits.
 74. A mammalian ribonuclease of claim68, wherein: (A) said activity is inhibited by NaCl; (B) said activityrequires Mg⁺⁺; and (D) said mammalian ribonuclease has an apaprentmolecular weight, as determined by SDS-PAGE, of about 50 to about 80kilodaltons.
 75. A mammalian ribonuclease of claim 68, wherein saidribonuclease is isolated from nucleii.
 76. A mammalian ribonuclease ofclaim 68, wherein said ribonuclease is isolated from cytosol.
 77. Themammalian protein of claim 68, wherein said ribonuclease is isolatablefrom human cells or tissues.
 78. A double-stranded RNA substratecomprising a duplex of a first oligonucleotide and a secondoligonucleotide, wherein (A) said first and said second oligonucleotideeach have a central portion having at least four consecutiveribofuranosyl residues having phosphodiester linkages, wherein saidcentral portions are base-paired with each otehr in said duplex; (B) atleast one of said first and said second oligonucleotides have portionsflanking said central portions having chemical modifications which makethem resistant to single-stranded nucleases.
 79. A double-stranded RNAsubstrate comprising a duplex of a first oligonucleotide and a secondoligonucleotide, wherein (A) said first and said second oligonucleotideeach have a central portion having at least four consecutiveribofuranosyl residues having phosphodiester linkages, wherein saidcentral portions are base-paired with each otehr in said duplex; (B) atleast one of said first and said second oligonucleotides have portionsflanking said central portions having chemical modifications which makethem resistant to single-stranded nucleases and increase their affinityfor the otehr oligonucleotide of the duplex.
 80. A double-stranded RNAsubstrate of claim 78, wherein said chemical modifications arephosphorothioate linkages or 2′-methoxy modifications.
 81. An affinitymatrix comprising the dsRNA substrate of claim
 78. 82. A method ofpurifying a ribonuclease or non-degradative RNA-binding proteincomprising contacting a sample containing said ribonuclease ornon-degradative RNA-binding protein with the affinity matrix of claim81.
 83. A synthetic oligomeric compound comprising, in sequence; a firstsegment having a plurality of 2′-O-alkyl nucleoside subunits beingjoined by phosphorothioate internucleoside linkages; and a secondsegment having at least four consecutive 2′-hydroxyl ribonucleosidesubunits being joined by phosphorothioate internucleoside linkages or byphosphodiester internucleoside linkages.
 84. A compound of claim 83further comprising a third segment having a plurality of 2′-O-alkylnucleoside subunits being joined by phosphorothioate internucleosidelinkages, said second segment being positioned in said oligomericbetween said first and said third segments.
 85. A compound of claim 83wherein said second segment has phosphodiester internucleoside linkages.86. A compound of claim 83 wherein said second segment hasphosphorothioate internucleoside linkages.
 87. A synthetic oligomericcompound comprising, in sequence; a first segment having a plurality of2′-O-alkyl nucleoside subunits being joined by phosphorothioateinternucleoside linkages; a second segment having at least fourconsecutive 2′-hydroxyl ribonucleoside subunits joined byphosphorothioate internucleoside linkages or by phosphodiesterinternucleoside linkages, and a third segment having a plurality of2′-O-alkyl nucleoside subunits being joined by phosphorothioateinternucleoside linkages.
 88. A compound of claim 87 wherein said secondsegment has phosphorothioate internucleoside linkages.
 89. Use of saidribonuclease of claim 68 for treating an organism having a diseasecharacterized by the undesired production of a protein encoded by saidmRMA.
 90. Use of said ribonuclease of claim 68 for identifying one ofsaid mRNA or a protein encoded by said mRNA.
 91. Use of saidribonuclease of claim 68 for diagnosing an aberrant state in an organismassociated with a protein encoded by said mRNA.
 92. A mammalianribonuclease having the activity of catalyzing the degradation of adouble stranded substrate wherein one of said strands of said substrateis a mRNA and the other of said strands comprises a compound of claim 1.93. A double-stranded RNA substrate of claim 78, wherein one of saidoligonucleotides has the nucleotide sequence of SEQ ID NO: 8.